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Accounting for Carbon Dioxide Emissions from Bioenergy Systems
Abstract
Researchers have recently argued that there is a 'critical climate accounting error' and that we should say 'goodbye to carbon neutral' for bioenergy. Many other analysts have published opionions on the same topic, and the US Environmental Protection Agency posted a specific call for information. The currently burning questions for carbon accounting is how to deal with bioenergy. The questions arises because, unlike for fossil fuels, burning of biomass fuels represents part of a cycle in which combustion releases back to the atmosphere carbon that was earlier removed from the atmosphere by growing plants. In a sustainable system, plants will again remove the carbon dioxide (CO) from the atmosphere. Conceptually, it is clear that there are no net emissions of the greenhouse gas CO if biomass is harvested and combusted at the same rate that biomass grows and removes CO from the atmosphere. The problem lies in the fact that growth and combustion do not occur at the same time or in the same place, and our accounting system boundaries - spatial and temporal - frequently do not provide full and balanced accounting. When the first comprehensive guidelines for estimating national greenhouse gas emissions and sinks were put together by the Organization for Economic Cooperation and Development, they noted that it has been argued that CO emissions resulting from bioenergy consumption should not be included in a country's official emission inventory because there are no net emissions if the biomass is produced sustainably, and if the biomass is not produced sustainably, the loss of carbon will be captured as part of the accounting for emissions from land-use change. In the same philosophical vein, the Kyoto Protocol provides that emissions or sinks of CO from land-use change and forestry activities be measured as the 'verifiable changes in carbon stocks'. From these has grown the convention that emissions from biomass fuels are generally not counted as part of emissions inventories, and biomass energy is sometimes referred to as being 'carbon neutral.' But what happens when a forest is harvested for fuel but takes 60 years to regrow or when biomass is harvested in a country that is not party to an international accord but is burned in a country that is party to an international accord? Biomass energy is only truly 'carbon neutral' if we get the system boundaries right. They need to make sure that the accounting methodology is compatible with our needs and realities in management and policy.
... Studies evaluating climate effects of forest-based bioenergy have produced divergent results due to inherent differences between bioenergy systems and different analytical approaches and assumptions (Cherubini et al., 2009). As discussed above, the choice of spatial system boundary and temporal scope is critical (Cherubini et al., 2009;Gustavsson et al., 2000;Marland, 2010;Schlamadinger et al., 1997) and should be coherent with the question studied (Koponen et al., 2018). Figure 3 illustrates alternative system boundaries that have been applied in studies of forest-based bioenergy. ...
... The UNFCCC reporting requirements specify that CO 2 emissions associated with biomass combustion are counted in the land use sector, that is, where the harvest takes place; they are therefore reported as zero in the energy sector to avoid double-counting (Goodwin et al., 2019). This reporting approach is accurate, has no gaps and does not assume that bioenergy is carbon neutral (Haberl at al., 2012;Marland, 2010), although it has sometimes been described as such (e.g. Norton et al., 2019;Searchinger et al., 2009). ...
The scientific literature contains contrasting findings about the climate effects of forest bioenergy, partly due to the wide diversity of bioenergy systems and associated contexts, but also due to differences in methods. The climate effects of bioenergy must be accurately assessed to inform policy‐making, but the complexity of bioenergy systems and associated land, industry and energy systems raises challenges for assessment. We examine misconceptions about climate effects of forest bioenergy and discuss important considerations in assessing these effects and devising measures to incentivise sustainable bioenergy as a component of climate policy. The temporal and spatial system boundary and the reference (counterfactual) scenarios are key methodology choices that strongly influence results. Focussing on carbon balances of individual forest stands, and comparing emissions at the point of combustion, neglect systems‐level interactions that influence the climate effects of forest bioenergy. We highlight the need for a systems approach, in assessing options and developing policy for forest bioenergy, that: 1) considers the whole life cycle of bioenergy systems, including effects of the associated forest management and harvesting on landscape carbon balances; 2) identifies how forest bioenergy can best be deployed to support energy system transformation required to achieve climate goals; and 3) incentivises those forest bioenergy systems that augment the mitigation value of the forest sector as a whole. Emphasis on short‐term emissions reduction targets can lead to decisions that make medium‐ to long‐term climate goals more difficult to achieve. The most important climate change mitigation measure is the transformation of energy, industry, and transport systems so that fossil carbon remains underground. Narrow perspectives obscure the significant role that bioenergy can play by displacing fossil fuels now, and supporting energy system transition. Greater transparency and consistency is needed in greenhouse has reporting and accounting related to bioenergy.
... Through photosynthesis, plants can capture the equivalent amount of CO 2 released to the atmosphere during combustion. Thus, there is no net increase in greenhouse gas emissions based on life-cycle analysis [8,9]. Presently, biomass plays a subordinate role to fossils in energy generation. ...
Porous silica was synthesized from cornhusk using the sol–gel polymeric route and compared with ash obtained from the direct combustion process under laboratory conditions. The unmodified ash from the direct combustion process was dissolved in NaOH for 1 h to form sodium silicate, which was subsequently hydrolyzed with citric acid to yield a silica xerogel. The obtained xerogel was characterized using inductively coupled plasma–optical emission spectrometry (ICP-OES), Fourier transforms infrared (FTIR) spectroscopy, X-ray diffraction (XRD), simultaneous thermal analysis (STA), gas sorption techniques to determine their elemental constituents, functional groups, crystalline phases, thermal stability, and porosity, respectively. The results showed that the synthesized silica xerogel exhibited porous network structures with a high-specific surface area and mesopore volume of 384 m²/g and 0.35 cm³/g, respectively. The pore size distribution revealed a complete transformation of the pore network structures of the unmodified ash from a monomodal to a bimodal pore system, with micro- and mesopore peaks centered around 1.5 and 3.8 nm, respectively. The ICP-OES results showed that the silica content significantly increased from 52.93 to 91.96 wt.% db after the sol–gel treatment. XRD diffraction confirmed the amorphicity of the silica particles obtained from the sol–gel extraction method. In addition, the STA data showed that the silica xerogel has high thermal stability compared to the unmodified ash, as the latter exhibited poor thermal stability and low textural properties. The high surface area and narrow pore cavity size distribution of the porous silica xerogel make it an ideal substrate for catalysts and an excellent template for growing other nanoparticles within the pores.
... These bands generally disappear during combustion as the significant share of organic compounds (i.e., cellulose, hemicellulose, and lignin) is decomposed as observed in in Figure 3 (bottom). The bands at approximately 1065, 972, and 1415 cm −1 are corresponding to the stretching vibration of CO 3 2− , which corresponds to the content of calcite (CaCO 3 ) in the ashes. The positions of the bands agree with the reference calcite in Figure 3 (bottom). ...
Featured Application: The synthesized biogenic silica can be considered in applications such as catalyst support, construction material, concrete and backing material. Abstract: Increased amounts of available biomass residues from agricultural food production are present widely around the globe. These biomass residues can find essential applications as bioenergy feedstock and precursors to produce value-added materials. This study assessed the production of biogenic silica (SiO 2) from different biomass residues in Africa, including cornhusk, corncob, yam peelings, cassava peelings and coconut husks. Two processes were performed to synthesize the biogenic silica. First, the biomass fuels were chemically pre-treated with 1 and 5% w/v citric acid solutions. In the second stage, combustion at 600 • C for 2 h in a muffle oven was applied. The characterization of the untreated biomasses was conducted using Inductively coupled plasma-optical emission spectrometry (ICP-OES), thermal analysis (TG-DTA) and Fourier-transform infrared spectroscopy (FTIR). The resulting ashes from the combustion step were subjected to ICP, nitrogen physisorption, Energy dispersive X-ray spectroscopy (EDX) as well as X-ray diffraction (XRD). ICP results revealed that the SiO 2 content in the ashes varies between 42.2 to 81.5 wt.% db and 53.4 to 90.8 wt.% db after acidic pre-treatment with 1 and 5 w/v% acid, respectively. The relative reductions of K 2 O by the citric acid in yam peel was the lowest (79 wt.% db) in comparison to 92, 97, 98 and 97 wt.% db calculated for corncob, cassava peel, coconut husk and cornhusk, respectively. XRD analysis revealed dominant crystalline phases of arcanite (K 2 SO 4), sylvite (KCl) and calcite (CaCO 3) in ashes of the biomass fuels pre-treated with 1 w/v% citric acid due to potassium and calcium ions present. In comparison, the 5 w/v% citric acid pre-treatment produced amorphous, biogenic silica with specific surface areas of up to 91 m 2 /g and pore volumes up to 0.21 cm 3 /g. The examined biomass residues are common wastes from food production in Africa without competition in usage with focus application. Our studies have highlighted a significant end-value to these wastes by the extraction of high quality, amorphous silica, which can be considered in applications such as catalyst support, construction material, concrete and backing material.
... Interest in Eucalyptus is supported by experience in Florida where E. grandis and E. amplifolia short rotation systems can produce up to 67 green Mg ha −1 year −1 in three years (Rockwood, 2012). The renewed interest in the USA in fast growing trees for bioenergy plantations (Perlack et al., 2011) has raised a number of questions as to sustainability (Williams et al., 2009;Vance et al., 2014;Robledo-Abad et al., 2017), carbon neutrality (Marland, 2010;Vanhala et al., 2013) and effects on biodiversity (Immerzeel et al., 2014;Tarr et al., 2017) as well as economic feasibility (McKenney et al., 2014;Ghezehei et al., 2015). The emergence of non-native Eucalyptus species as potential bioenergy crops has engendered additional questions including biological feasibility and potential invasiveness (Gordon et al., 2012;Callaham et al., 2013), effects on wildfire behavior (Goodrick and Stanturf, 2012), and water consumption (Vose et al., 2015;Maier et al., 2017). ...
Renewed interest in non-native Eucalyptus species for planting in the southern US has been spurred by projections suggesting they are more productive than the widely cultured Pinus species, by warming temperatures, and by attempts to identify frost-tolerant species as well as developing genetically modified Eucalyptus for frost tolerance. In addition to questions of environmental suitability, the economic viability of Eucalyptus is a significant hurdle to widespread adoption for commercial plantings. We sought to assess the potential obtainable yields and economic feasibility of Eucalyptus grandis Hill ex. Maiden and E. benthamii Maiden et Cambage, two species suitable for the southern United States. Using the process-based growth model 3PG, we projected potential yields at the sub-county level for E. grandis in Florida where it is operationally grown and E. benthamii in USDA Plant Hardiness Zones 8a and 8b where it has shown tolerance to occasional low temperatures. The 3PG model estimated mean annual volume increment, inside bark (MAI) that was used to estimate land expectation value (LEV) and internal rate of return (IRR). The MAI of E. grandis ranged from 18 to 119 m 3 ha −1 year −1 (9 to 59.5 dry Mg ha −1 year −1) with a mean of 42.6 m 3 ha −1 year −1 (20.8 dry Mg ha −1 year −1) for sites in peninsular Florida. The lower growth projections came from north Florida areas where annual frosts occur. Excluding urban areas, the LEV of E. grandis ranged from 1710 ha −1 with a mean of -2707 ha −1 to $1532 ha −1. The maximum estimated IRR was 15.9%. Our results show that Eucalyptus is potentially profitable as a bioenergy crop in the southern USA, but potential profitability of E. benthamii was limited by low temperature; positive LEV was obtained where productivity was 30 m 3 ha −1 year −1 or more. Profitability was restricted to a small percentage (12%) of sites theoretically within the operational range in the southern U.S. indicating that a wholesale conversion of Pinus taeda plantations is unlikely.
... But there 153 is no limit to land use emissions from developing countries ( Searchinger et al. 2009;UNFCCC 154 2002). Thus, the carbon neutral assumption is problematic when biomass is imported from a 155 developing country and burned in a developed country ( Marland 2010). Therefore, the carbon8 neutral assumption in this protocol should be treated with caution, and the accounting system 157 should be modified for consistency. ...
This study presents a critical analysis regarding the assumption of carbon neutrality in life cycle assessment (LCA) models that assess climate change impacts of bioenergy usage. We identified a complex of problems in the carbon neutrality assumption, especially regarding bioenergy derived from forest residues. In this study, we summarized several issues related to carbon neutral assumptions, with particular emphasis on possible carbon accounting errors at the product level. We analyzed errors in estimating emissions in the supply chain, direct and indirect emissions due to forest residue extraction, biogenic CO2 emission from biomass combustion for energy, and other effects related to forest residue extraction. Various modeling approaches are discussed in detail. We concluded that there is a need to correct accounting errors when estimating climate change impacts and proposed possible remedies. To accurately assess climate change impacts of bioenergy use, greater efforts are required to improve forest carbon cycle modeling, especially to identify and correct pitfalls associated with LCA accounting, forest residue extraction effects on forest fire risk and biodiversity. Uncertainties in accounting carbon emissions in LCA are also highlighted, and associated risks are discussed.
... The Intergovernmental Panel on Climate Change (IPCC) has recommended that the carbon dioxide directly emitted from landfill covers and released from combusting landfill biogas be considered part of the natural carbon cycle of the earth (biogenic carbon dioxide); hence, they do not have any effect on increase of GHG emissions in the atmosphere (IPCC, 2006). Even though the IPCC recommendation is being followed in this paper, Marland (2010) and Johnson (2009) have concluded that there is a "critical climate accounting error" and now is a suitable time to say "big goodbye to carbon neutral" for bioenergy or CO 2 release from solid waste decomposition. The currently hot question for carbon accounting is how to deal with waste decomposition, biomass combustion and bioenergy. ...
As methane constitutes about 50% of landfill biogas, reduction of methane emissions from municipal solid waste (MSW) landfills results in climate change mitigation. As such, it is important for a landfill lifetime model to properly reflect the manner in which biogas is managed. The goal of this research is to compare landfill biogas management in a conventional landfill with a bioreactor landfill during a 100-year time horizon. This comparison concentrates on the greenhouse gas (GHG) emissions balances and electricity generation potential from recovered biogas using reciprocating internal combustion engines (RICE), which leads to avoiding GHG emissions due to fossil fuel displacement. The results estimated that the total amount of GHG emissions released to atmosphere, including fugitive methane emissions and the avoided effect of electrical energy production, was 668 and 803 kg carbon dioxide (CO 2) equivalents (CO 2 E) per metric ton (t) of landfilled MSW for the conventional and the bioreactor landfill, respectively. This study underscores the importance of installing an aggressive gas collection system early for bioreactor landfills, and for investigating methods of improving gas collection efficiency during active landfilling.
... The Intergovernmental Panel on Climate Change (IPCC) has recommended that the carbon dioxide directly emitted from landfill covers and released from combusting landfill biogas be considered part of the natural carbon cycle of the earth (biogenic carbon dioxide); hence, they do not have any effect on increase of GHG emissions in the atmosphere (IPCC, 2006). Even though the IPCC recommendation is being followed in this paper, Marland (2010) and Johnson (2009) have concluded that there is a "critical climate accounting error" and now is a suitable time to say "big goodbye to carbon neutral" for bioenergy or CO 2 release from solid waste decomposition. The currently hot question for carbon accounting is how to deal with waste decomposition, biomass combustion and bioenergy. ...
As methane constitutes about 50% of landfill biogas, reduction of methane emissions from municipal solid waste (MSW) landfills results in climate change mitigation. As such, it is important for a landfill lifetime model to properly reflect the manner in which biogas is managed. The goal of this research is to compare landfill biogas management in a conventional landfill with a bioreactor landfill during a 100-year time horizon. This comparison concentrates on the greenhouse gas (GHG) emissions balances and electricity generation potential from recovered biogas using reciprocating internal combustion engines (RICE), which leads to avoiding GHG emissions due to fossil fuel displacement. The results estimated that the total amount of GHG emissions released to atmosphere, including fugitive methane emissions and the avoided effect of electrical energy production, was 668 and 803 kg carbon dioxide (CO2) equivalents (CO2E) per metric ton (t) of landfilled MSW for the conventional and the bioreactor landfill, respectively. This study underscores the importance of installing an aggressive gas collection system early for bioreactor landfills, and for investigating methods of improving gas collection efficiency during active landfilling.
... The inconsistencies are especially pronounced with the use of different system boundaries, assumptions, and accounting practices for similar fuel pathways [10] and subsequently interfere with our understanding of biofuels. These inconsistencies raise questions about how LCA should inform production as well as policy maker decisions [21]. ...
At the core of the debate over life-cycle assessment (LCA) modeling of the environmental impacts of biofuels is doubt that biofuels can mitigate climate change. Two types of LCA, attributional and consequential, have been applied to answer this question with competing results. These results turn on system boundary design, including feedstock considerations and assumptions of indirect land-use impacts. The broadening of the system boundary to include large scale land-use change of biofuel production has challenged the viability of biofuels to meet climate change goals. This paper reviews some of the latest literature in biofuels LCA exemplary of this debate and discusses the distinctions between attributional and consequential models in biofuels. We also present a generalized boundary map that can be used to convey LCA system boundaries clearly and succinctly within both attributional and consequential LCA.
... Gate User natives. Recent methodological discussions also include carbon soil change and the timing of emissions [106][107][108][109]. When biomass grows, it absorbs CO 2 from the atmosphere [73,[110][111][112]. ...
On a global scale, bioenergy is highly relevant to renewable energy options. Unlike fossil fuels, bioenergy can be carbon neutral and plays an important role in the reduction of greenhouse gas emissions. Biomass electricity and heat contribute 90% of total final biomass energy consumption, and many reviews of biofuel Life Cycle Assessments (LCAs) have been published. However, only a small number of these reviews are concerned with electricity and heat generation from biomass, and these reviews focus on only a few impact categories. No review of biomass electricity and heat LCAs included a detailed quantitative assessment. The failure to consider heat generation, the insufficient consideration of impact categories, and the missing quantitative overview in bioenergy LCA reviews constitute research gaps. The primary goal of the present review was to give an overview of the environmental impact of biomass electricity and heat. A systematic review was chosen as the research method to achieve a comprehensive and minimally biased overview of biomass electricity and heat LCAs. We conducted a quantitative analysis of the environmental impact of biomass electricity and heat. There is a significant variability in results of biomass electricity and heat LCAs. Assumptions regarding the bioenergy system and methodological choices are likely reasons for extreme values. The secondary goal of this review is to discuss influencing methodological choices. No general consensus has been reached regarding the optimal functional unit, the ideal allocation of environmental impact between co-products, the definition of the system boundary, or how to model the carbon cycle of biomass. We concluded that a higher level of transparency and a harmonisation of the preparation of biomass electricity and heat LCAs are needed to improve the comparability of such evaluations.
... Another matter of discussion between policies and the use of forest is the definition of 'bioenergy'. On the other hand, the emissions from biomass fuels are usually not calculated as part of emissions accounts and biomass energy is sometimes referred to as being 'carbon neutral' (Marland, 2010). ...
The aim of the paper is to offer a systemic overview about some critical and interdependent relations among carbon offset, carbon sequestration and carbon stock. Rooting in the complexity perspective, the work discusses some relevant measurement methods and financial issues related to the land use - land use change forestry (LULUCF) applied under Kyoto Protocol rules. There are uncertainties on the estimation on carbon flux owing to the application of various models of estimates. The study also focuses on the credits of forestry projects, which can be sold or purchased on the carbon market. In conclusion, the work sheds light on the complex side of decision processes in framing and selecting models to estimate the carbon balance under the Kyoto Protocol target. The opportunity for investment in forest projects depends on the cost management of the projects themselves, and the price between wood market and unit carbon.
... One of the earliest misconceptions about the effects of forest bioenergy is the erroneous conclusion that forest bioenergy is carbon neutral because forests harvested for bioenergy eventually grow back, reabsorbing carbon emitted during energy combustion. Although the flaw in this assumption has been identified repeatedly (e.g., Marland 2010, Agostini et al. 2013, some government documents, forest industry reports, and websites claim that forest bioenergy is carbon neutral because forests regrow. One such statement among many found on the worldwide web is as follows: ...
Critical errors exist in some methodologies applied to evaluate the effects of using forest biomass for bioenergy on atmospheric greenhouse gas emissions. The most common error is failing to consider the fate of forest carbon stocks in the absence of demand for bioenergy. Without this
demand, forests will either continue to grow or will be harvested for other wood products. Our goal is to illustrate why correct accounting requires that the difference in stored forest carbon between harvest and no-harvest scenarios be accounted for when forest biomass is used for bioenergy.
Among the flawed methodologies evaluated in this review, we address the rationale for accounting for the fate of forest carbon in the absence of demand for bioenergy for forests harvested on a sustained yield basis. We also discuss why the same accounting principles apply to individual stands
and forest landscapes.
... Through this chain of reasoning, it should become clear what Gregg Marland meant when he stated that " biomass energy is only 'carbon neutral' if we get the system boundaries right " (Marland 2010, p. 866). The motivating question for his research approach was: " What happens when a forest is harvested for fuel but takes 60 years to regrow or when biomass is harvested in a country that is not party to an international accord but is burned in a country that is? " (ibid). ...
Basically, the combustion of woody biomass in high temperature processes results in a long lasting addition of carbon dioxide to the atmosphere. When harvesting large extra amounts of stem tree for energetic use, a global as well as secular time frame is needed to assess overall conse-quences if due attention is to be given to biosphere processes, including the complex productivity of whole ecosystems. Analytically, a time dependent variable of carbon neutralization can be traced by a simple carbon neutrality or CN factor. Using the (forgotten) Marland approach, project manag-ers should document how a pay-back of the whole carbon debt incurred by their projects proceeds over time. As recommended by the European Parliament in May 2011, this methodology should be applied consistently in climate and energy policies when revising the failures of the 'instant carbon neutrality' approach for smokestack emissions that was propagated within the Kyoto process, the first phase of which is ending in 2012. Otherwise, we allow that the substitution of wood pellets for coal or other fossil fuels creates long lasting extra emissions of carbon dioxide. This is a climate policy mistake which carbon trading systems such as that of the EU ETS do not compensate for, but instead amplify by giving extra credits for further pollution. This contradicts the very purpose of the UNFCCC, namely to prevent environmental degradation.
... Zanchi et al., 2012) suggest that the exclusion of mineral soil C in forest C flux analysis can result in not fully accounting for the C flux under specific forest management or site conditions. These results also emphasize the importance of considering sufficiently long temporal scales in forest C flux analysis (Marland, 2011). Forest management alternatives that result in a delayed or avoided release of GHGs might be more effective in mitigating climate change relative to a scenario characterized by high, although short-term, CO 2 emissions. ...
Forest carbon cycles play an important role in efforts to understand and mitigate climate change. Large amounts of carbon (C) are stored in deep mineral forest soils, but are often not considered in accounting for global C fluxes because mineral soil C is commonly thought to be relatively stable. We explore C fluxes associated with forest management practices by examining existing data on forest C fluxes in the northeastern US. Our findings demonstrate that mineral soil C can play an important role in C emissions, especially when considering intensive forest management practices. Such practices are known to cause a high aboveground C flux to the atmosphere, but there is evidence that they can also promote comparably high and long-term belowground C fluxes. If these additional fluxes are widespread in forests, recommendations for increased reliance on forest biomass may need to be reevaluated. Furthermore, existing protocols for the monitoring of forest C often ignore mineral soil C due to lack of data. Forest C analyses will be incomplete until this problem is resolved.
... biomass harvested for bioenergy and then regrown). This is a reasonable assumption for fast growing species, but may not apply in the case of biofuels from slower growing biomass, like forests (Johnson, 2009;Marland, 2010). A forest may take up to 100 years to regrow, and the system can be defined C neutral only at the end of proper time boundaries: CO 2 is emitted in one point in time when biomass is burnt but the sequestration in the new vegetation is spread over several years, depending on the specific rotation period. ...
Carbon dioxide (CO2) emissions from biomass combustion are traditionally assumed climate neutral if the bioenergy system is carbon (C) flux neutral, i.e. the CO2 released from biofuel combustion approximately equals the amount of CO2 sequestered in biomass. This convention, widely adopted in life cycle assessment (LCA) studies of bioenergy systems, underestimates the climate impact of bioenergy. Besides CO2 emissions from permanent C losses, CO2 emissions from C flux neutral systems (that is from temporary C losses) also contribute to climate change: before being captured by biomass regrowth, CO2 molecules spend time in the atmosphere and contribute to global warming. In this paper, a method to estimate the climate impact of CO2 emissions from biomass combustion is proposed. Our method uses CO2 impulse response functions (IRF) from C cycle models in the elaboration of atmospheric decay functions for biomass-derived CO2 emissions. Their contributions to global warming are then quantified with a unit-based index, the GWPbio. Since this index is expressed as a function of the rotation period of the biomass, our results can be applied to CO2 emissions from combustion of all the different biomass species, from annual row crops to slower growing boreal forest.
Renewable biomass plays a crucial role in transitioning toward climate-friendly heating sources; however, not without its collateral damage in terms of the disproportionately high effects on local air quality. The associated proliferation of residential heating appliances around the world, including developed regions like Europe, where an estimated 70 million are housed, does not appear to be abating. Here, we identify super self-concentrating ambient pollution events whereby solid-fuel residential heating haze is infused with a hitherto unaccounted for firelighter smoke that contributes additional adsorbing black carbon. This black carbon-organic aerosol combination results in a strong positive radiative forcing (up to 149 W m−2) and alters the boundary layer thermodynamics sufficiently so as to further suppress pollutant dilution and dispersion leading to extraordinary high submicron particulate matter (PM1: 166 µg m−3). Unfortunately, there is no silver lining in this cloud until the promotion of solid biomass fires with firelighters for ignition is replaced by a co-benefit policy.
Utility wood pellets (wood pellets) are a densified biomass fuel that can generate electricity or heating when burned. Production, consumption, and trade of wood pellets have grown substantially since the late 2000s in a small number of countries. The locus of consumption growth is industrial power plants where wood pellets are frequently used for co-firing with, or replacement of, coal. The catalytic factors for the robust wood pellet expansion have been European Union (EU) climate change policies and incentives, particularly designating the product as a 'renewable energy,' assessing their carbon emissions as zero, and providing financial support. The United States, with its sizeable forests and timber plantations, reacted by intensifying wood pellet production for export, primarily to the United Kingdom and several EU member states. In 2021, U.S. wood pellet exports reached $1 billion for the first time. Wood pellet consumption is also rising in Asia with South Korea and Japan, driven by their own climate change policies, incentivizing rapid recent growth in imports. This paper examines the rise of wood pellets as an alternative energy source and traded commodity in the era of climate change.
Reference mass spectra are routinely used to facilitate source apportionment of ambient organic aerosol (OA) measured by aerosol mass spectrometers. However, source apportionment of solid-fuel-burning emissions can be complicated by the use of different fuels, stoves, and burning conditions. In this study, the organic aerosol mass spectra produced from burning a range of solid fuels in several heating stoves have been compared using an aerosol chemical speciation monitor (ACSM). The same samples of biomass briquettes and smokeless coal were burnt in a conventional stove and Ecodesign stove (Ecodesign refers to a stove conforming to EU Directive 2009/125/EC), while different batches of wood, peat, and smoky coal were also burnt in the conventional stove, and the OA mass spectra were compared to those previously obtained using a boiler stove. The results show that although certain ions (e.g., m/z 60) remain important markers for solid-fuel burning, the peak intensities obtained at specific m/z values in the normalized mass spectra were not constant with variations ranging from < 5 % to > 100 %. Using the OA mass spectra of peat, wood, and coal as anchoring profiles and the variation of individual m/z values for the upper/lower limits (the limits approach) in the positive matrix factorization (PMF) analysis with the Multilinear Engine algorithm (ME-2), the respective contributions of these fuels to ambient submicron aerosols during a winter period in Dublin, Ireland, were evaluated and compared with the conventional a-value approach. The ME-2 solution was stable for the limits approach with uncertainties in the range of 2 %–7 %, while relatively large uncertainties (8 %–29 %) were found for the a-value approach. Nevertheless, both approaches showed good agreement overall, with the burning of peat (39 % vs. 41 %) and wood (14 % vs. 11 %) accounting for the majority of ambient organic aerosol during polluted evenings, despite their small uses compared to electricity and gas. This study, thus, accounts for the source variability in ME-2 modelling and provides better constraints on the primary factor contributions to the ambient organic aerosol estimations. The finding from this study has significant implications for public health and policymakers considering that it is often the case that different batches of solid fuels are often burnt in different stoves in real-world applications.
Bioenergy, i. e. energy extracted from biomass, is often seen as a promising substitute
for fossil energy. Reviews from the natural and ecological sciences state that bioenergy
resource assessment is a particularly complex subject. It needs to factor possible
conflicts with other land uses, forecast increases in agricultural productivity
and project food demands over time. Regionally differentiated bioenergy assessments
are moreover extremely sensitive to the local context and political choices. Instead,
our literature review considers the actual global total utilisation of biomass and its
maximum capacity for all human purposes together. These are not reported in the
usual energy statistics run by the UN and other organisations. From those few global
studies that exist in the (typically non-economic) literature it becomes apparent that
bioenergy today is a small part of total biomass consumption, only, and that the main
body of biomass is consumed in form of nutrition and organic materials for artefacts
like clothes, furniture or tools.The analysed literature including recent studies of the
global „ecological footprint“ reveals not only that the energy content of today’s biomass
utilisation is in the same order of magnitude as total primary energy consumption,
but also that about twenty to forty percent of total terrestrial organic nature is
already appropriated by humankind.
Growing international trade in wood pellets is one response to regional efforts to mitigate the global problem of climate change. With this growing use of wood energy, there is increased scrutiny of the associated environmental impacts and concern over possible unintended consequences (e.g., nonrenewable energy inputs) that may detract from the carbon savings provided by such renewable energy sources. The focus of this article is to present an accounting system for the embodied fossil fuels in wood energy systems. This system is based on life-cycle assessment methodology and could accommodate fairly the variability in fossil fuel inputs for various bioenergy systems. Such a system could be incorporated into biofuel subsidies or carbon taxation policies. We use three scenarios as examples to illustrate (1) that wood-to-energy systems entail the use of fossil fuels and that the amount of this "embodied fossil carbon" varies with the processing inputs and transportation required and (2) that carbon tax/biofuel subsidies can be adjusted to accommodate variations in embodied fossil carbon. The growth in life-cycle databases and the advent of environmental product declarations make embodied fossil fuel calculations such as those presented here an increasingly practical component of biofuels policy development.
In spite of the benefits associated with the production and consumption of biofuels, there are some crucial debatable issues like high cost, food insecurity, etc., that put them to the negative side. However, biofuels still hold impressive market potentials in the world today though most of their production technologies are sophisticated and costly. Liquid biofuels like bioethanol and biodiesel are commonly produced from feedstocks like corn, rapeseed, soybean, etc., but there are other potential feedstocks, which are more sustainable like palm oil. This chapter discusses the major sources of biofuel feedstocks, types of biofuels, their production technologies, and global market potentials.
The definition of baselines is a major step in determining the greenhouse-gas emissions of bioenergy systems. Accounting frameworks with a planning objective might require different baseline attributes and designs than those with a monitoring objective.
Electricity generated from woody biomass material is generally considered renewable energy and carbon neutral. However, this has recently been criticized by scientists, who argue that the greenhouse gas (GHG) emission profile of bioenergy is nuanced and the carbon neutral label is inappropriate. An initial carbon debt is created when a forest is harvested and combusted for bioenergy. Because forests regrow over a period of years, life cycle analyses show that bioenergy generated from whole trees from forests may not reduce GHG emissions in the short term, as is required to combat climate change. State renewable portfolio standards and federal laws and proposed legislation designed to incentivize renewable energy typically define eligible forms of biomass that qualify for these incentives. Most of these definitions are very broad and do not account for GHG emissions from bioenergy. Federal and state laws should incorporate life cycle analyses into definitions of eligible biomass so that these laws incentivize biomass electricity that reduces GHG emissions in the next several decades.
Use of biomass‐based electricity and hydrogen in alternative transport could provide environmentally sustainable transport options with possible improvements in greenhouse gas balance. We perform a life cycle assessment of electric vehicle (EV) and fuel cell vehicle (FCV) powered by bioelectricity and biohydrogen, respectively, derived from Norwegian boreal forest biomass, considering the nonclimate neutrality of biological carbon dioxide (CO2) emissions and alteration in surface albedo resulting from biomass harvesting—both with and without CO2 capture and storage (CCS)—while benchmarking these options against EVs powered by the average European electricity mix. Results show that with due consideration of the countering effects from global warming potential (GWP) factors for biogenic CO2 emissions and change in radiative forcing of the surface for the studied region, bioenergy‐based EVs and FCVs provide reductions of approximately 30%, as compared to the reference EV powered by the average European electricity mix. With CCS coupled to bioenergy production, the biomass‐based vehicle transport results in a net global warming impact reduction of approximately 110% to 120% (giving negative GWP and creating a climate‐cooling benefit from biomass use). Other environmental impacts vary from −60% to +60%, with freshwater eutrophication showing maximum reductions (40% for the EV case and 60% for the FCV case) and photochemical oxidation showing a maximum increase (60% in the FCV value chain).
This chapter examines the controls on radiocarbon (14C) content of CO2 in the atmosphere over time. It discusses atmospheric observations and their interpretation using models of atmospheric transport, which describe the physical mixing of the atmosphere. This spans the simplest conceptual model of addition of a gas into a single well-mixed box of air, to multi-box models with three-dimensional global or regional atmospheric transport models. This format is applied to atmospheric history for five different time periods when different factors dominated atmospheric 14C.
Bioenergy from forest residues can be used to substitute fossil energy sources and reduce carbon emissions. However, increasing biomass removals from forests reduce carbon stocks and carbon input to litter and soil. The magnitude and timeframe of these changes in the forest carbon balance largely determine how effectively forest biomass reduces greenhouse gas emissions from the energy sector and helps to mitigate climate change. This paper reviews the impacts of harvest-residue-based bioenergy on the carbon balance of forests and discusses aspects linked to the concept of carbon neutrality. This type of forest bioenergy will reduce the emissions in a long run but near-term reductions depend essentially on the longevity of the residues used.
In Life Cycle Assessment (LCA), carbon dioxide (CO2) emissions from biomass combustion are traditionally assumed climate neutral if the bioenergy system is CO2 flux neutral, i.e. the quantity of CO2 released approximately equals the amount of CO2 sequestered in biomass. This convention is a plausible assumption for fast growing biomass species, but is inappropriate for slower growing biomass, like forests. In this case, the climate impact from biomass combustion can be potentially underestimated if CO2 emissions are ignored, or overestimated, if biogenic CO2 is considered equal to anthropogenic CO2. The estimation of the effective climate impact should take into account how the CO2 fluxes are distributed over time: the emission of CO2 from bioenergy approximately occurs at a single point in time, while the absorption by the new trees is spread over several decades. Our research target is to include this dynamic time dimension in unit-based impact analysis, using a boreal forest stand as case study. The boreal forest growth is modelled with an appropriate function, and is investigated under different forestry regimes (affecting the growth rate and the year of harvest). Specific atmospheric decay functions for biomass-derived CO2 are then elaborated for selected combinations of forest management options. The contribution to global warming is finally quantified using the GWPbio index as climate metric. Results estimates the effects of these practices on the characterization factor used for the global warming potential of CO2 from bioenergy, and point out the key role played by the selected time horizon.
Radiative forcing impacts due to increased harvesting of boreal forests for use as transportation biofuel in Norway are quantified using simple climate models together with life cycle emission data, MODIS surface albedo data, and a dynamic land use model tracking carbon flux and clear-cut area changes within productive forests over a 100-year management period. We approximate the magnitude of radiative forcing due to albedo changes and compare it to the forcing due to changes in the carbon cycle for purposes of attributing the net result, along with changes in fossil fuel emissions, to the combined anthropogenic land use plus transport fuel system. Depending on albedo uncertainty and uncertainty about the geographic distribution of future logging activity, we report a range of results, thus only general conclusions about the magnitude of the carbon offset potential due to changes in surface albedo can be drawn. Nevertheless, our results have important implications for how forests might be managed for mitigating climate change in light of this additional biophysical criterion, and in particular, on future biofuel policies throughout the region. Future research efforts should be directed at understanding the relationships between the physical properties of managed forests and albedo, and how albedo changes in time as a result of specific management interventions.
The accounting now used for assessing compliance with carbon limits in the Kyoto Protocol and in climate legislation contains
a far-reaching but fixable flaw that will severely undermine greenhouse gas reduction goals (1). It does not count CO2 emitted from tailpipes and smokestacks when bioenergy is being used, but it also does not count changes in emissions from
land use when biomass for energy is harvested or grown. This accounting erroneously treats all bioenergy as carbon neutral
regardless of the source of the biomass, which may cause large differences in net emissions. For example, the clearing of
long-established forests to burn wood or to grow energy crops is counted as a 100% reduction in energy emissions despite causing
large releases of carbon.
Rules for applying the Kyoto Protocol and national cap and trade laws contain a major, but fixable, carbon accounting flaw in assessing bioenergy. The accounting now used for assessing compliance with carbon limits in the Kyoto Protocol and in climate legislation contains a far-reaching but fixable flaw that will severely undermine greenhouse gas reduction goals (1). It does not count CO 2 emitted from tailpipes and smokestacks when bioenergy is being used, but it also does not count changes in emissions from land use when biomass for energy is harvested or grown. This accounting erroneously treats all bioenergy as carbon neutral, regardless of the source of the biomass, which may cause large differences in net emissions. For example, the clearing of long-established forests to burn wood or to grow energy crops is counted as a 100% reduction in energy emissions despite causing large releases of carbon. Several recent studies estimate that this error, applied globally, would create strong incentives to clear land as carbon caps tighten. One study (2) estimated that a global CO 2 target of 450 ppm under this accounting would cause bioenergy crops to expand to displace virtually all the world's natural forests and savannahs by 2065, releasing up to 37 gigatons (Gt) of CO 2 per year (comparable to total human CO 2 emissions today). Another study predicts that, based solely on economic considerations, bioenergy could displace 59% of the world's natural forest cover and release an additional 9 Gt of CO 2 per year to achieve a 50% "cut" in greenhouse gases by 2050 (3). The reason: When bioenergy from any biomass is counted as carbon neutral, economics favor large-scale land conversion for bioenergy regardless of the actual net emissions (4).
Globalization and the dynamics of ecosystem sinks need be considered in post-Kyoto climate negotiations as they increasingly
affect the carbon dioxide concentration in the atmosphere. Currently, the allocation of responsibility for greenhouse gas
mitigation is based on territorial emissions from fossil-fuel combustion, process emissions and some land-use emissions. However,
at least three additional factors can significantly alter a country’s impact on climate from carbon dioxide emissions. First,
international trade causes a separation of consumption from production, reducing domestic pollution at the expense of foreign
producers, or vice versa. Second, international transportation emissions are not allocated to countries for the purpose of
mitigation. Third, forest growth absorbs carbon dioxide and can contribute to both carbon sequestration and climate change
protection. Here we quantify how these three factors change the carbon dioxide emissions allocated to China, Japan, Russia,
USA, and European Union member countries. We show that international trade can change the carbon dioxide currently allocated
to countries by up to 60% and that forest expansion can turn some countries into net carbon sinks. These factors are expected
to become more dominant as fossil-fuel combustion and process emissions are mitigated and as international trade and forest
sinks continue to grow. Emission inventories currently in wide-spread use help to understand the global carbon cycle, but
for long-term climate change mitigation a deeper understanding of the interaction between the carbon cycle and society is
needed. Restructuring international trade and investment flows to meet environmental objectives, together with the inclusion
of forest sinks, are crucial issues that need consideration in the design of future climate policies. And even these additional
issues do not capture the full impact of changes in the carbon cycle on the global climate system.
Forest and bioenergy strategies offer the prospect of reduced CO2 emissions to the atmosphere. Such strategies can affect the net flux of carbon to the atmosphere through 4 mechanisms: storage of C in the biosphere; storage of C in forest products; use of biofuels to displace fossil-fuel use; use of wood products which often displaces other products that require more fossil fuel for their production. We use the mathematical model GORCAM (Graz/Oak Ridge Carbon Accounting Model) to examine these mechanisms for 16 land-use scenarios. Over long time intervals the amount of C stored in the biosphere and in forest products reaches a steady state and continuing mitigation of C emissions depends on the extent to which fossil fuel use is displaced by the use of bioenergy and wood products. The relative effectiveness of alternative forest and bioenergy strategies and their impact on net C emissions strongly depend, for example, on the productivity of the site, its current usage, and the efficiency with which the harvest is used. When growth rates are high and harvest is used efficiently, the dominant opportunity for net reduction in C emissions is seen to be fossil-fuel displacement. At the growth rates and efficiencies of harvest utilization adopted in many of our base scenarios, the net C balance at the end of 100 years is very similar whether trees are harvested and used for energy and traditional forest products, or reforestation and forest protection strategies are implemented. The C balance on a plantation system that provides a constant output of biomass products can look different than the balance of a single parcel of land.
The current framework through which greenhouse gas emissions and removals in the land use sector are accounted under the Kyoto Protocol has several problems. They include a complex structure, onerous monitoring and reporting requirements, and potential for omission of some important fluxes. One solution that may overcome some of these problems is to include all lands and associated processes within a country's jurisdiction, rather than restrict accounting to specific nominated land categories or activities. Ideally, the accounting approach should cover all significant biospheric sources and sinks, avoid biased or unbalanced accounting, avoid leakage and require no arbitrary adjustments to remedy unintended consequences. Furthermore, accounting should focus on the direct human-induced component of biospheric emissions/removals so that debits/credits can be allocated equitably and provide appropriate incentives to adopt land-use management options with beneficial outcomes for the atmosphere.
Most guidance for carbon footprinting, and most published carbon footprints or LCAs, presume that biomass heating fuels are carbon neutral. However, it is recognised increasingly that this is incorrect: biomass fuels are not always carbon neutral. Indeed, they can in some cases be far more carbon positive than fossil fuels.This flaw in carbon footprinting guidance and practice can be remedied. In carbon footprints (not just of biomass or heating fuels, but all carbon footprints), rather than applying sequestration credits and combustion debits, a ‘carbon-stock change’ line item could be applied instead. Not only would this make carbon footprints more accurate, it would make them consistent with UNFCCC reporting requirements and national reporting practice.There is a strong precedent for this change. This same flaw has already been recognised and partly remedied in standards for and studies of liquid biofuels (e.g. biodiesel and bioethanol), which now account for land-use change, i.e. deforestation. But it is partially or completely missing from other studies and from standards for footprinting and LCA of solid fuels.Carbon-stock changes can be estimated from currently available data. Accuracy of estimates will increase as Kyoto compliant countries report more land use, land use change and forestry (LULUCF) data.
Estimation of greenhouse gas emissions and sinks: Final report from the OECD experts meeting 18-21
- Oecd