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Burli et al. (2016). “Switchgrass-based bioenergy,” BioResources 11(3), 7102-7123. 7102
Sustainability Protocols and Certification Criteria for
Switchgrass-Based Bioenergy
Pralhad Burli,a,* Pankaj Lal,a Bernabas Wolde,a and Janaki Alavalapati b
Production of bioenergy from cellulosic sources is likely to increase due to
mandates, tax incentives, and subsidies. However, unchecked growth in
the bioenergy industry has the potential to adversely influence land use,
biodiversity, greenhouse gas (GHG) emissions, and water resources. It
may have unintended environmental and socioeconomic consequences.
Against this backdrop, it is important to develop standards and protocols
that ensure sustainable bioenergy production, promote the benefits of
biofuels, and avoid or minimize potential adverse outcomes. This paper
highlights agronomic information on switchgrass, a high-potential
bioenergy feedstock, and the role of specialized certification programs.
The existing sustainability standards and protocols were reviewed in order
to identify key gaps that justify a certification program specifically for
switchgrass-based bioenergy. The criteria and indicators that should be
considered for such a certification program are outlined.
Keywords: Bioenergy; Certification; Sustainability; Protocols; Indicators; Switchgrass
Contact information: a: Department of Earth and Environmental Studies, Montclair State University, 1
Normal Avenue, Montclair, NJ 07043, USA; b: School of Forestry and Wildlife Sciences, Auburn
University, 3301 Forestry and Wildlife Building, 602 Duncan Drive, Auburn, AL 36849 – 3418, USA;
* Corresponding author: burlip1@montclair.edu
INTRODUCTION
Among alternative energy sources, biofuels such as switchgrass-based ethanol have
emerged as a favored option because they can address prevailing concerns about fossil fuel
use and the belief that the transition will be relatively easy from a technological and
infrastructure perspective. In addition, sizeable biomass yield and high carbohydrate
content indicate that biofuels produced from switchgrass can compete favorably against
other feedstocks from an economic perspective (McLaughlin and Kszos 2005; Daystar et
al. 2013). Although US petroleum imports in 2014 were at their lowest level in
approximately three decades, they fulfilled 27% of the country’s petroleum needs (EIA
2015). Thus, the production of biofuels has the potential to enhance a country’s energy
security by limiting petroleum imports while supporting domestic agricultural markets,
boosting industrial activity, and possibly reducing environmental impacts through
greenhouse gas (GHG) reductions, when undertaken responsibly. Federal policies,
including the 2005 Energy Policy Act and the 2007 Energy Independence Security Act
(EISA), have encouraged the production of cellulosic biofuels, i.e., fuels produced from
energy grasses such as switchgrass and other woody biomaterials.
The United States ranked first in terms of annual investment and net capacity
additions for biofuel production for both biodiesel and fuel ethanol in 2015 (REN21 2016).
While biofuel production is likely to increase due to production mandates, tax incentives,
and subsidies, if not implemented with care it could also cause some undesirable impacts.
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Burli et al. (2016). “Switchgrass-based bioenergy,” BioResources 11(3), 7102-7123. 7103
Studies have highlighted the potential adverse impacts of bioenergy production in several
areas, including land use and biodiversity (Firbank 2008), GHG emissions (Searchinger et
al. 2008), socio-economic ramifications (German et al. 2011), and the availability of water
resources (Berndes 2002). It is important to ensure that opportunities for new activities in
the field of bioresources do not come at the cost of nature, the environment, and society
(Cramer 2007). Accordingly, it is crucial to consider the environmental, social and
economic impacts of promoting biofuel production and consumption along the entire
supply chain, ranging from production of raw materials to its intended use as a fuel.
A potential approach to ensure sustainable biofuel production is the establishment
of certification criteria (Hunt and Forster 2006). This research highlights production and
agronomic information on switchgrass use in bioenergy production, the role of certification
programs, a review of existing programs, the identification of key gaps that justify a
specialized certification program, and potential criteria and indicators that may be
considered. We use the case of switchgrass to highlight important components of a robust
certification program and develop a template that can be adapted for other bioenergy
feedstocks. The first section highlights the agronomy of switchgrass, its ecological
services, and its potential as a biofuel feedstock. The next section presents an analysis of
conventional biomass production and marketing certification programs. Potential gaps that
underscore the need for specialized sustainability criteria and indicators for switchgrass are
identified and followed by a description of the opportunities presented by such a
certification program. The subsequent section presents criteria and indicators for a
switchgrass-based biofuel certification program. The final section addresses the future
research and outreach needs for increased use of switchgrass as a bioenergy feedstock and
the implementation of a certification program.
Why Switchgrass-based Bioenergy?
Switchgrass (Panicum virgatum) is a perennial high-fiber grass, native to the tall-
grass prairie of the U.S., except for California and the Pacific Northwest region (Vogel et
al. 2004). It grows in a wide range of agronomic conditions, including dry and poorly
drained soils, shallow and dry soils, as well as shores, riverbanks, marshes, and oak and
pine woodlands. It can grow in various soil types and in soils with pH levels ranging from
4.5 to 7.6 and with little to no fertilizer application (Hanson and Johnson 2005; Rinehart
2006). While switchgrass does not require much water (Casler et al. 2004), it also is highly
resistant to pests and diseases (Vogel et al. 2004). It can grow in areas susceptible to
flooding, facilitate habitat protection, and create winter wildlife cover and nesting areas
(Wright 2007; Liebig et al. 2005; Varvel et al. 2008). The deep root system also provides
other ecosystem services, such as greater soil organic carbon storage in underground
biomass at greater depth, rather than near the surface where it is susceptible to
mineralization and loss (Frank et al. 2004; Liebig et al. 2005; Lee et al. 2007). Switchgrass
also reduces surface water velocity and enhances infiltration. It can also serve as a
windbreak for field crops, as well as mitigate run-off from agricultural fields (Liebig et al.
2005).
Currently, switchgrass is cultivated in the US for pasture and hay to feed livestock
(McLaughlin et al. 2005). The US Department of Energy identified switchgrass as a high
potential energy grass because of its adaptability and yield potentials (Wright 2007).
Switchgrass does not have the annual establishment and fertilization needs of corn,
soybean, and other crops that have been considered for biofuel production. Switchgrass
increases the amount of organic matter in the soil, while reducing soil carbon release
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Burli et al. (2016). “Switchgrass-based bioenergy,” BioResources 11(3), 7102-7123. 7104
associated with annual site establishment. This reduces the cost associated with purchase,
transport, and management of seedlings, while enhancing net energy performance, which
could result in a better overall GHG performance (Tilman et al. 2006; Vadas et al. 2008;
Varvel et al. 2008). With minimal boiler retrofitting needs, switchgrass can be co-fired
with coal in thermal plants (Mitchell et al. 2012). Moreover, the limited need for
specialized equipment, especially for on-farm activities ranging from cultivation to harvest,
to manage switchgrass cultivation does not impose additional costs and enhances its overall
economic viability.
Switchgrass plantations can produce as much as 16 tons of dry biomass per acre
under good management in the wetter southeastern regions. Comparatively, the drier
Northern plains have a different cultivar with lower yields. Roughly 80 gallons of ethanol
can be produced per dry ton of feedstock (Mitchell et al. 2012). Additional benefits of
using switchgrass as a biofuel feedstock include avoiding the food/fuel controversy, not
competing for prime agricultural land and making use of otherwise unusable land while
restoring its quality for other uses (Sanderson et al. 1996). Potentially, switchgrass-based
bioenergy can add to the broader socioeconomic and environmental benefits associated
with a growing bioenergy sector. Benefits include the diversification of feedstock portfolio
and supplemental income to landowners, creation of local jobs and tax revenue that
revitalizes rural economics, the ability to meet growing energy services demand at lower
environmental costs, and a reduction in the dependence on petroleum imports for energy
supply.
METHODS
Analysis of Existing Frameworks
There are numerous certification programs for agriculture, forest output, and
biomass that are currently being implemented or developed. These programs include the
American Tree Farm System, Basic Criteria for Responsible Soy Production, Protocol for
Fresh Fruit and Vegetables, Program for the Endorsement of Forest Certification,
International Sustainability and Carbon Certifications (ISCC), Global Bio-Pact, Ethical
Trading Initiative, Fair Trade Labeling Organizations International, Flower Labeling
Program, Forest Stewardship Council (FSC), Green Gold Label, International Federation
of Organic Agriculture Movement, Principles and Criteria for Sustainable Palm Oil
Production, Sustainable Agricultural Standards, Sustainable Forestry Initiative, and
Roundtable on Sustainable Biofuels (RSB), etc. These certification programs feature
common sustainability criteria, such as biodiversity, agrochemical application, and the
impact on soil and water. Despite these similarities, they also exhibit differences in the
number, depth, and type of criteria involved, which highlight differentiated priorities.
While these impact categories represent the main drivers and concerns in the current
certification efforts, there are several additional performance-related criteria and
indicators, including GHG emissions and air pollution performance, which require more
attention.
Meanwhile, enhanced computing capacity allows for the evaluation of large
collections of reports, peer-reviewed journal articles, working papers, etc., using text
analysis and text visualization tools. Text mining borrows techniques from several fields,
including linguistics, computational statistics, and computer science (Meyer et al. 2008).
Word clouds and word frequency charts depict representative keywords contained in a set
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Burli et al. (2016). “Switchgrass-based bioenergy,” BioResources 11(3), 7102-7123. 7105
of documents being studied or analyzed (Cui et al. 2010). Apart from providing a visual
representation, frequency charts and word clouds also demonstrate key ideas and important
themes contained within published literature.
In this paper, a text analysis was performed using the computing software R
(Williams 2016) on important standards and certification guidelines such as the RSB, FSC,
ISCC, as well as reports published by the Council on Sustainable Biomass Production
(CSBP), Biomass Technology Group, and the group on Sustainable Production of Biomass.
In addition, academic literature, including the papers by Lewandowski and Faaij (2006),
Van Dam et al. (2008), Lee et al. (2008), Lal et al. (2011), the 2013 discussion paper by
Annalisa Zezza on Sustainability Certification in the Biofuel Sector, and the working paper
by Devereaux and Lee (2009) were analyzed. The text mining algorithm uses a procedure
called Stemming, which removes common word endings such as ‘s,’ ‘es,’ ‘ed,’ etc.
(Williams 2016). In Fig. 1, there is a word cloud that provides a visual of the 100 most
frequently used words in the papers previously listed. Figure 2 depicts the absolute
frequency of the words that appear more than 400 times in these papers and documents.
The frequencies of the words will likely increase with the number of papers included in the
analysis. This analysis and visual representation provides insights about some of the major
focus areas for certification criteria and production standards that have been published
previously. While the text analysis highlights important key-words and is useful for
illustrative purposes, the text analysis and word cloud was followed by in-depth review of
existing standards and certification criteria.
Fig. 1. Word cloud representing the 100 most-frequent words in the text analysis
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Burli et al. (2016). “Switchgrass-based bioenergy,” BioResources 11(3), 7102-7123. 7106
Fig. 2. Words appearing more than 400 times in the cumulative text analysis
Table 1A. Snapshot of Different Certification Programs on Select Criteria to
Highlight the Range of Coverage and Specificity
Roundtable on Sustain-
able Biomaterials (RSB)
Renewable Energy
Initiative (RED)
Renewable Fuel Standard
Program (RFS2)
Greenhouse
Gas
Emissions
On average 50% savings
compared to fossil fuel
baseline, and progressive
improvements over time
35% savings for all
biofuels progressing
to 50% and 60% by 1
Jan 2017 and 1 Jan
2018 respectively
Different savings criteria
based on biofuel category:
Cellulosic ethanol: 60%
Biomass-based diesel: 50%
Renewable Fuel: 20%
Land Use
change
Multiple criteria ranging
from consent of local
communities, food security
impacts, impact on
endangered species,
property rights, etc.
Restrictions on
conversion of highly
biodiverse lands, high
carbon stock lands,
and peatlands
Planted crops/trees and
residues restricted to lands
cleared/cultivated prior to
December 2007
Soil and
Water
Guidelines aimed at
enhancing/maintaining
physical, chemical, and
biological properties of soil
as well as quality and
quantity of surface and
ground water
No specific
guidelines; Member
states that are
significant source of
biofuels or raw
materials must report
national measures
No specific guidelines,
however, impacts to date
and likely future impacts to
be assessed and reported
every 3 years
Sources: RSB (2013); Alberici et al. (2014)
Biomass certification programs exhibit differences in terms of generalizability, end
use specificity, and applicability across the supply chain. They also differ in terms of the
chains of custody they operate; different versions including fully segregated through the
supply chain or mass balance with percentage of approved raw material use indicated in
the final product. Differences also exist in the advancement of the certification efforts for
different energy crops, including those that have reached advanced stages (Round Table
on Sustainable Palm Oil), those that are in progress (Round Table on Sustainable Soy and
Better Sugarcane Initiative), to those that have yet to be initiated (wheat, sugar beet,
switchgrass, and rapeseed) (Vis et al. 2008).
804 728 650
540 529 450 434
0
100
200
300
400
500
600
700
800
900
biomass certif product system sustain develop criteria
Word
Frequency
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Table 1B. Criteria, Guidelines, and Indicators for Land Use and Competition with
Food Crops
Criteria and Guidelines
1.1 Minimize conversion of potentially fertile land to growing switchgrass or setting up
conversion/processing facilities.
1.2 Ensure that diversion of land to a switchgrass dedicated farm does not infringe on food
production and lead to propagation of monocultures.
1.3 Biomass production should not result in irrecoverable losses to above ground
vegetation or carbon sinks and should be supported with documentation showing a
positive net benefit from reduced material and energy use over the lost opportunity of
using the land for other productive uses.
1.4 Biomass production should not result in a substantial loss of soil carbon; for example
peatland, wetland, and mangrove cultivation.
1.5 The practice of growing switchgrass for bioenergy should adhere to socially
established agronomic and operational norms of agricultural production and avoid
competing local community out of the land market.
Indicators
1.1 Net GHG emission change comparing previous land use to current use.
1.2 Documentation of changes to land use patterns and information of overall crop mix.
1.3 Documentation of changes to local/regional land prices and comparison with past
trends.
1.4 Documentation of changes to local/regional food output and prices, and comparison
with past trends.
Sources: Rinehart 2006; Casler et al. 2007; Cramer et al. 2007; Mitchell et al. 2008; Varvel et
al. 2008; Vogel et al. 2008; Mitchell et al. 2012; NRDC 2014.
Standards and certification measures can evaluate various aspects of biomass
production. There is a lot of variety in the main objectives they pursue, such as ensuring
safety, establishing liability, or differentiating products. Additionally, they can measure the
extent of the burden and benefit conferred on different applicants, such as small-scale
farmers compared to large-scale incorporated farms. Certifications vary in the number,
type, and detail of criteria given; the type of biomass production system (forest, energy
crop, power sector, emissions trading) (Vis et al. 2008); regional scope (international as in
the Forest Stewardship Council, or country/regional as in the Sustainable Forest Initiative)
(Cramer et al. 2007); breadth of the structure (umbrella structure or national systems);
hectares of land currently covered by the certification program; and the scope of their
efforts, such as a stand-alone certification, such as the International Sustainability and
Carbon Certifications, or the development and harmonization of different biomass
production system certification protocols as in the Global Bio-Pact (Ladanai and
Vinterbäck 2010).
Need for a Specialized Certification Program for Switchgrass-Based
Biofuels
Development of feedstock specific standards and protocols provides a potential
pathway to maximize the advantages of a certification program. While some standards and
criteria from existing programs can be incorporated, such as those for feedstock cultivation
and management, energy balances, GHG emission reductions, biomass harvesting,
transport and conversion, the opportunity to account for specific requirements of different
feedstock can result in substantial gains. New and specialized certification protocols could
be important additions to generic biomass certification protocols by creating new criteria
and indicators, broadening the base of biomass production covered, and ensuring the
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Burli et al. (2016). “Switchgrass-based bioenergy,” BioResources 11(3), 7102-7123. 7108
sustainable production and marketing of biomass. In addition to meeting long-term
sustainability objectives through the implementation of sustainability criteria and
indicators through a certification program, growers may benefit from charging premiums,
building consumer confidence, and communicating the responsible sourcing of their
product. These benefits may justify the burden of compliance (Ladanai and Vinterbäck
2010). Furthermore, implementation, verification, and monitoring are key factors for
ensuring long-term success (Scarlat and Dellemand 2011).
The agronomics for different biofuel feedstock entail different management
practices and outcomes (Mitchell et al. 2012). As such, the impact of crop agriculture,
forest biomass, energy crops, such as switchgrass, on the physical, biological, and chemical
properties of soil, hydrology and water quality, site productivity and regenerative capacity,
landscape, ecosystem, species, genetic biodiversity, net carbon sequestration and non-
carbon greenhouse gases release, and socioeconomic performance cannot be assumed to
be the same. Each factor may require different mitigation approaches and corresponding
specialized criteria and indicators certifying the sustainable production of that feedstock
(Stupak et al. 2011). The currently available biomass certification programs do not
specifically address switchgrass-based bioenergy as a product; the agronomic
recommendations do not specifically address switchgrass as a bioenergy feedstock separate
from other types of biomass, or even the hay and forage end use of switchgrass production
(Mitchell et al. 2008). This lack of clarity could reduce transparency and increase conflict
in meeting the economic, ecological, and social sustainability criteria and inherent
tradeoffs. For example, winter switchgrass harvesting enables higher biomass recovery,
stand productivity, and persistence, and it reduces the availability of nitrogen in the
biomass that enhances conversion efficiency and its overall economic performance
(Mitchell et al. 2012). Delaying harvest until spring provides nesting and winter wildlife
cover that enhances its ecological performance, but results in lower yields (Vogel et al.
2002; Adler et al. 2006). Such tradeoffs are better accounted for in specialized certification
programs.
Despite some common management and harvesting practices, the different
objectives of bioenergy farming through the maximization of dry material, compared to
maximizing quality when switchgrass farming is practiced for the purpose of foraging,
leads to inherently different variations in farm management, harvest, and storage practices
(Mitchell et al. 2008). Thus, featuring the growth of switchgrass for bioenergy feedstock
in farmland management plans and relevant certification programs is merited (Vis et al.
2008; Ladanai and Vinterbäck 2010). Open-ended biomass certification programs such as
the initial Round Table on Sustainable Palm Oil (RTPO), which did not specify end use,
missed the opportunity to avoid unintended impacts such as using drained peat lands to
grow palm trees for bioenergy. This created a substantial net CO2 loss from using bioenergy
(Vis et al. 2008). By accounting for the end use of the biomass key indicators, such as
lifecycle GHG balance, net energy balance and eligible land use-related criteria should be
featured in certification protocols. Compared to generic and open-ended certification
protocols, switchgrass and bioenergy end-use specialized certification programs mitigate
ambiguity, account for distinct attributes, contribute to a more transparent conduct, and
enhance the overall effectiveness of certification processes (Cramer et al. 2007; Vis et al.
2008). The potential for the sector’s growth notwithstanding, there is limited experience
in large-scale switchgrass production for bioenergy purposes. This results in many
unknowns, and the creation of a standard protocol is strategic.
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More specialized best-management practices and agronomic recommendations can
be featured in these protocols, unlike a generic, all-encompassing biomass production or
marketing sustainability certification protocol. These protocols allow for switchgrass-
specific criteria and indicators and ensure sustainable switchgrass production for bioenergy
use. For instance, clearly articulating specialized criteria and indicators creates an
opportunity to plan for contingencies, such as the potential invasiveness of switchgrass in
large-scale monoculture energy plantations, especially in areas where switchgrass is a non-
native crop (Rinehart 2006).
Its application can also have spillover effects, where switchgrass growers apply or
adapt these protocols to other farm practices. This can include practices such as livestock
and agroforestry management, increasing the overall acreage of biomass production, and
the breadth of farm practice conducted sustainably.
A switchgrass-focused certification protocol gives enforcement agencies relevant
metrics to govern an emerging industry and assess the adherence of farmers to
predetermined principles (Cramer et al. 2007). Currently, there are limited energy and
environmental policies in the United States that explicitly account for switchgrass and
corresponding sustainability certification protocols. This provides an opportunity for the
creation of a specialized set of criteria and indicators (Cramer et al. 2007). Beside the
synergistic benefits of covering the broader attributes of switchgrass production and
warranting higher levels of sustainability, the integration of a specialized certification
program and relevant energy and environmental policies could support these standards.
Additionally, there is an opportunity for increased integration between agricultural
production of energy crops, such as switchgrass, and energy certification protocols (Vis et
al. 2008; Ladanai and Vinterbäck 2010). This can improve upon and expand coverage of
green electricity certification efforts, such as Green-e, which consider all energy crops as
eligible for renewable electricity certification, given that they have less than a 10-year
rotation cycle, do not displace food production, and do not use land that has been farmed
in the previous two years (Green-e 2014).
Such efforts can be scaled up by making up for the limited number of eligibility
criteria and indicators and by expanding the number of states where the program runs.
Through specialized criteria and indicators, such certification protocol can be better
integrated with the emissions trading schemes to create a mutually reinforcing synergy of
an energy services that has a lower carbon footprint while potentially directing more funds
towards the industry’s growth (Ladanai and Vinterbäck 2010).
Specialized certifications create opportunities for greater integration of
environmental and bioenergy development programs, such as the Biomass Crop Assistance
Program (BCAP). BCAP provides financial incentives to growers of biomass crops to turn
it into bioenergy feedstock. Additionally, the Conservation Reserve Program (CRP)
encourages environmentally beneficial practices through the conservation and restoration
of sites. This can take the form of integrating CRP enrollment eligibility criteria and
performance standards from the certification program to ensure higher levels of
sustainability, while also providing additional incentives that benefit growers and the
bioenergy industry alike. Similarly, other environmental programs focusing on such
aspects as biodiversity can be integrated with such a certification scheme for a synergistic
effect that enhances dual outcomes.
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RESULTS AND DISCUSSION
Suggested Criteria, Guidelines, and Indicators
The criteria developed in this paper build on existing standards and certification
protocols to build specific guidelines for switchgrass-based biofuels. They are informed by
agronomic recommendations for growing switchgrass as a bioenergy feedstock and attempt
to balance the high-yield objective with broader economic, ecological, and social
considerations.
These criteria and indicators are not necessarily exclusive of one another. For
example, land use enhancement measures may also have profitability implications. The
criteria and indicators presented here highlight the unique attributes, opportunities, and
challenges of switchgrass that should be featured in the specialized certification protocol
and should encompass other general biomass sustainability production standards. This
includes the overall contribution to the enhancement of social, economic, and
environmental wellbeing through criteria and indicators dealing with labor conditions,
local job creation, and protection of vulnerable areas. We attempted to delineate both
quantitative and qualitative criteria and indicators covering the entire lifecycle, beginning
with land use and the cultivation of the raw materials, to the end use of the product and
waste disposal. While some prescribed elements can be applied generally and guide
relevant policies, others can be adapted to specific regional circumstances and other
contextual variations to account for heterogeneity. These guidelines should incorporate
feedback from key stakeholder groups in order to enhance their acceptance and
implementation.
The impact categories include land use change and competition with food crops,
agrochemical application, site establishment and harvest, biodiversity, water, waste
management, economic sustainability, local and/or regional prosperity and social well-
being, air quality and GHG emissions, as well as monitoring and verification. The criteria
and guidelines shed light on the proposed objectives under each impact category, whereas
the indicators present potential pathways to adhere to the prescribed course of action and
encompass measurable outcomes and/or qualitative indicators that can be evaluated over
time.
Land use change and competition with food crops
The development of switchgrass-based biofuels at a viable commercial scale that
ensures a reliable and consistent feedstock supply for a conversion facility will require
large areas of land for switchgrass cultivation (Rinehart 2006; Mitchell et al. 2012).
Moreover, the land requirement for setting up preprocessing and conversion facilities is
likely to be substantial (NRDC 2014). Factors such as former land use and land cover, site
productivity, and terrain suitability, will affect the sustainability of potential large-scale
land use change.
Agrochemical application
Switchgrass cultivation practices will likely limit the use of agrochemicals and will
reduce ecological impacts as a result. Cultivators must adopt practices to ensure the
efficient use of nutrients, maintain the quality of soil, provide greater resources and
coverage for microbes, and reduce the need for agrochemical application. With these
guidelines, cultivators can utilize sustainable alternatives and minimize unintended
consequences of rampant agrochemical use.
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Table 2. Criteria, Guidelines, and Indicators for Agrochemical Application
Criteria and Guidelines
2.1 Perform soil test at potential root depth to test for soil pH, availability of phosphorous,
potassium and other nutrient availability to assess if it is within range and to take
corrective measures.
2.2 Limit N application and adapt use to suit site fertility, timing of establishment, plant N
fixing ability, and availability of legumes that fix N. Reduce presence of Nitrogen in
biomass to help conversion efficiency of cellulose into fermentable sugar and reduces air
potential air pollution associated with combusting biomass with high nitrogen presence.
2.3 Periodically test for N and other nutrient abundance in the root zone soil profile and its
infiltration to groundwater.
2.4 Reduce presence of residue from previous land use and weed seed in the root depth soil
profile to reduce revival during fertilization and application of other nutrients.
2.5 Adapt application rate and timing to cultivar, other management practices, precipitation,
and soil and site characteristics.
2.6 Use growing season or cool season specific chemicals and prescribed by local best
management practice application rates per acre.
2.7 Minimize use of herbicidal control and adopt adequate weed control management
techniques during establishment to reduce requirements in the following years and limit
weed competition for resources with switchgrass to improve stand success.
Indicators
2.1 Documentation indicating tests that identify optimal application rates ensuring minimal or
no run-off and infiltration to groundwater systems.
2.2 Rotation cycle readings on pH, soil nutrient content test.
Sources: Martin et al. 1982; Muir et al. 2001; Vogel et al. 2001; Vogel et al. 2002; Hanson et al.
2005; Fike et al. 2006; Mulkey et al. 2006; Cramer et al. 2007; Lee et al. 2007; Mitchell et al.
2008; Mitchell et al. 2012; NRDC 2014.
Establishment and harvest
Switchgrass requires about three years to become established and to reach full yield
potential. Therefore, cultivators must continue to follow updated best management
practices (BMPs) to enhance biomass yield. Establishment rates and yield vary based on
region, switchgrass variety, and ecotype (Wright 2007).
Cultivators should seek guidance about region-specific cultivars based on the latest
breeding and genetics research, and their specific hardiness zone to avoid winter stand loss,
attain optimal flowering time, and reduce economic risk. They should also follow stated
BMPs in regards to the portion of the harvest that should be left on the ground as an organic
nutrient source for subsequent years.
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Table 3. Criteria, Guidelines, and Indicators for Stand Establishment and
Harvest
Criteria and Guidelines
3.1 Establish through no-till planting and minimize use of conventional tillage and drill planting.
If drill establishment is required, documentation should show that the tradeoff in cost, soil
quality, and net energy balance change should justify such establishment method.
3.2 Renovate stand with higher yielding material if stand success rate is low by reestablishing
stand with different input and management techniques to ensure full term high yield stand
starting from the panting year.
3.3 Harvest in annual or biannual cycles to ensure survivability and productivity. If conservation
land is used to grow switchgrass, then delayed harvest may be considered. Allow for full
senescence before winter harvest to reduce fertilization needs.
3.4 Harvest a few inches above ground to minimize disturbance to winter cover and nesting
function of the switchgrass cropland and to avoid disturbing the soil organic carbon (SOC)
storage at deep root levels.
3.5 Ensure that harvest levels do not exceed minimum critical biomass density per area and to
maintain integrity of the soil stability, organic matter richness, and continued SOC storage.
3.6 Stalk bale in uniform sizes to ease arrangement for storage, save on space and volume
per weight, help transportation cost, utilize all space available, eases management,
maximize use employment of existing baling, handling, hauling, and processing systems
without an expensive retrofitting or specialized equipment. This practice enhances
volume per weight for storage and transportation purposes, and reduces pre- processing
drying need.
3.7 Store harvest in an enclosed area or cover with hay trap to limit biomass quality loss,
spoilage, and maintenance of extractable ethanol content.
Indicators
3.1 Quantity of dry matter weight loss and changes in moisture content.
3.2 Quantity of SOC storage and soil organic matter at switchgrass root levels.
3.3 Percentage of potential production that can be harvested the year of planting and number
of years before full potential production is achieved.
3.4 Saving on time, fuel, labor and other costs and trend in establishment and management
cost.
3.5 Adherence to harvesting and storage guidelines to meet conversion facility procurement
requirements
Sources: Panciera et al. 1984; Vogel et al. 1987; Wiselogel et al. 1996; Sanderson et al. 1997;
Smart et al. 1997; Martinez-Reyna and Vogel 2002; Vogel et al. 2002; Frank et al. 2004; Vogel
et al. 2004; Bransby et al. 2005; Liebig et al. 2005; Vogel et al. 2005; Fike et al. 2006; Schmer et
al. 2006; Perrin et al. 2008.
Biodiversity
Conserving and maintaining species diversity, native habitats, and ecosystems are
important responsibilities that have been repeatedly safeguarded through legislative
statutes (NRDC 2014). Switchgrass is an excellent habitat for wildlife species because it
provides suitable nesting sites and protection from predators (Renz 2009). As noted in
Cramer et al. (2007), it is important that plantations not be located near areas of high
conservation value or in areas that have high natural and/or cultural value. The primary
goal is to maintain habitat integrity and stimulate growth in an effort to minimize impact
on plant community diversity.
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Table 4. Criteria, Guidelines, and Indicators for Biodiversity
Criteria and Guidelines
4.1 Plantations should not be established in areas switchgrass is not native to or should be
done with the extra responsibility of ensuring no or minimal impact takes place in terms
of becoming weedy or invasive or displacing other local vegetation and negatively
affecting the background ecosystem’s stability.
4.2 Minimize interference with regular maintenance and spread of wildlife; avoid
fragmentation of unique habitats, and ecological corridors.
4.3 Preparation of conservation plan to include plan for protection/enhancement of
species/ecosystems that are likely to be impacted.
4.4 Monitor for outbreak of grasshoppers, leafhoppers, switchgrass moth, and armyworms
and other common switchgrass pests around switchgrass plantations. Participants must
demonstrate preparedness for response to potential disease, insect pest, and
invasiveness of switchgrass associated with large-scale dedicated plantations.
4.5 Minimize the chances of such outbreak by using pathogen screened and certified seeds.
4.6 Maintain regular communication channel with local extension workers for region specific
updates on outbreaks and other updates on agronomics and best management practices.
4.7 Place restrictions on biomass harvest during critical breeding/hatching season.
Indicators
4.1 Monitor trends in local biodiversity index.
4.2 Monitor ecological corridors and provision of appropriate surrounding buffer zones where
necessary.
4.3 Periodic evaluation of conservation plan to assess adherence to plan objectives.
4.4 Frequency and impact of plantation on overall community’s agricultural stand,
productivity, yield and quality level resulting from pest outbreaks and switchgrass
invasiveness.
4.5 Frequency and acreage of controlled burning in a rotation cycle.
Sources: Sanderson et al. 1996; McLaughlin et al. 1998; McLaughlin et al. 2002; Casler et al.
2004; Masters et al. 2004; Vogel et al. 2004; Roth et al. 2005; Cramer et al. 2007; Lal et al.
2011; NRDC 2014.
Water Switchgrass is a flood- and drought-resistant energy grass and as such, it requires
less water than traditional row crops. While the specific water requirement for switchgrass
biofuels may vary with the agricultural intensity and conversion technology adopted, water
is an important resource both in the production and conversion processes (Earth Institute
2011). For example, switchgrass planted in the floodplains provides limited stress on
already scarce water resources, but it also mitigates problems of soil erosion (Bardhan and
Jose 2012). Global certification standards and biofuel policies emphasize the importance
of sustainable water use and the protection of water bodies (Van Dam et al. 2008). Not
paying adequate attention to the water requirements along the biofuel supply chain could
result in negative consequences for the economic prosperity and health of local
communities (NRDC 2014). The production of biofuels from switchgrass must not deplete
surface or ground water while maintaining the quality of water.
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Table 5. Criteria, Guidelines, and Indicators for Water
Criteria and Guidelines
5.1 Preparation of a comprehensive water management plan including estimates on water
requirements, availability, and usage by cultivators and conversion facilities.
5.2 Frameworks to avoid contamination of ground and surface water resources.
5.3 Documentation of existing characteristics of local water sources including physical and
chemical attributes to serve as a baseline.
5.4 Treatment of wastewater containing contaminants that can impact human or ecosystem
health including wildlife, soil, and water resources.
Indicators
5.1 Evidence indicating adherence to federal/state BMPs.
5.2 Periodic assessment of physical and chemical attributes of local water resources to ensure
maintenance of baseline characteristics, ensuring that non-renewable water sources are
not are not depleted or contaminated.
5.3 Steps taken for reusing or recycling wastewater, demonstration of improvement in water
efficiency.
Sources: Cramer et al. 2007; Lal et al. 2011; RSB 2013; NRDC 2014.
Waste Management
Agricultural and industrial processes result in a range of by-products and waste
material that must be handled appropriately. Careful handling ensures that the production
of biofuels does create unintended environmental damages and problems.
Table 6. Criteria, Guidelines, and Indicators for Waste Management
Criteria and Guidelines
6.1 Develop recycling strategies and minimum waste plans or “zero waste” goals.
6.2 Minimize risk of damage to environment and human life through proper storage,
handling, and disposal of chemicals and hazardous wastes as well as microbes/catalysts
uses in biofuel operations according to federal regulations and guidelines.
Indicators
6.1 Demonstrate material efficiency improvements in feed stock production and conversion
processes.
6.2 Document evidence indicating compliance with regulations pertaining to storage, handling,
and disposal of chemicals and hazardous wastes.
Sources: RSB 2013; NRDC 2014.
Economic sustainability, local/regional prosperity, and social well-being
The biofuels industry, along its entire product life cycle, provides the potential to
boost agriculture and industrial activity and to create domestic employment in both direct
and indirect pathways. However, the financial viability of feedstock production or
conversion processes is central to the long-term sustainability of the industry (NRDC
2014). Furthermore, the benefits associated with the development of a new industry should
reach individuals engaged directly, such as employees and local communities (Cramer et
al. 2007). As a result, the specific socioeconomic impacts as well as direct and indirect
contributions the local/regional economy should be measured using simple input-output
models or freely available tools such as the Jobs and Economic Development Impact
(JEDI) model developed by the National Renewable Energy Laboratory (NREL).
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Table 7. Criteria, Guidelines, and Indicators for Economic Sustainability,
Prosperity, and Social Well-Being
Criteria and Guidelines
7.1 Stream of income over rotation cycle should indicate preferable return compared to other
land uses and biomass production.
7.2 Progress towards competitive pricing of switchgrass compared to other feedstock through
cost reducing measures as using marginal land or other land with lower opportunity cost
7.3 Contribution of the bioenergy industry to spur local economic activities
7.4 No negative influence on working conditions, land/property rights and human rights
Indicators
7.1 Trend of acreage enrolled in land devoted solely to switchgrass cultivation or through
intercropping.
7.2 Profit per acre on cultivation and harvest for switchgrass
7.3 Direct economic value created, number of direct jobs (local and regional) and approximate
indirect jobs attributable to the industry.
7.4 Trends in average work hours, per capita income and local/regional income inequality
attributable to bioenergy related activities
7.5 Number of land/property ownership conflicts
Sources: Rinehart 2006; Cramer et al. 2007; Mitchell et al. 2008; Perrin et al. 2008; Lal et al.
2011; Mitchell et al. 2012; NRDC 2014.
Air quality and GHG emissions
The transition towards biofuels is designed to mitigate the negative effects of fossil
fuel dependence. Therefore, it is important to consider the local air quality and global GHG
emission that result from biofuel use. While some of the criteria mentioned in Table 1B,
such as land use change, will contribute to the GHG balance, it is important to specify
standards that focus on GHG emissions and air quality. In addition, using Life Cycle
Analysis (LCA) tools, such as GREET, could be useful to strengthen the measurement
aspects associated with GHG emission reductions.
Table 8. Criteria, Guidelines, and Indicators for Air Quality and GHG Emissions
Criteria and Guidelines
8.1 Evaluation of emissions and criteria pollutants from cultivation and conversion processes
and development of air management plan
8.2 Lifecycle GHG emissions for switchgrass-based biofuels should be lower than the
associated fossil fuel baseline
Indicators
8.1 Reduction of GHG emissions by 50-70 percent for electricity production and 60 percent
for biofuels with periodic reviews to match global best practices
8.2 Annual report of air emissions and comparison with baseline
8.3 Third party audits of GHG lifecycle inventory and emission estimates
Sources: Cramer et al. 2007; RSB 2013; NRDC 2014.
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Monitoring and verification
As part of the endeavor toward sustainable production of switchgrass-based
bioenergy, periodic internal audits of the certification, and subsequent external audits, are
encouraged to affirm management’s commitment to employees through the entire process
of biomass and biofuel production. This includes biomass/biofuel handling, transport,
storage, conversion, distribution supply chain, sub-contractors, and end users. The audit
should evaluate attainment of continued compliance and operational targets. The audit
should aim to build on measures that contribute to greater compliance and/or take
corrective and preventive actions to ensure an active engagement in sustainability
practices.
Table 9. Criteria, Guidelines, and Indicators for Monitoring and Verification
Criteria and Guidelines
9.1 Periodic internal and external audits to ensure adherence to targets and guidelines
9.2 Public dissemination of certification protocol related obligations and audit results publicly
available
Indicators
9.1 Availability of internal/external audit reports pertaining to the product life-cycle in publicly
accessible formats such as print or on the organization website
Sources: Cramer et al. 2007; Ismail et al. 2011.
Documents submitted in support of the application, and those detailing the results
of the latest internal and external audits, must be produced and must account for a
substantial portion of the total biomass/biofuel production transactions completed by the
applicant. The application should be subjected to tests of internal consistency and reviewed
by external accreditors. The certification system and the applicant may use these standards
to evaluate compliance trends over the duration, identification, and targeting of operational
challenges and opportunities that are better captured by long- term data. Collection of this
data can help realign the criteria and indicators to practical issues and considerations that
surface over time.
Furthermore, information provided by a supplier regarding its product, technology,
price and other details, should be accurate, up-to-date and relevant. Attributes of the
product supply chain, ranging from feedstock cultivation, conversion, and end-use, that
ensure long-term sustainability and environmental stewardship, should be articulated in the
monitoring process. The claim of product compliance with certification standard should be
based on the final bioenergy product that is derived from certified switchgrass.
Discussion and Future Work
The agronomy and conversion of switchgrass into bioenergy is not identical to that
of other feedstocks. This demonstrates the need for and presents an opportunity to develop
switchgrass-specific criteria and indicators that account for its agronomic attributes,
incorporate best management practices from other biofuel certification systems, and are
rigorous yet practical from an implementation perspective. The target of such standards
and protocols is to ensure development of switchgrass-based bioenergy that realizes the
potential benefits of second-generation bioenergy, while safeguarding from the potential
adverse outcomes. These standards complement existing standards and regulations, and
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provide specialized criteria and indicators to relevant stakeholders. This will build
consumer confidence and provide credibility to an industry that is still in its nascent stages
of development. It will also build acceptance for the product across the supply chain,
including the handling, transport, storage, and distribution. The recommended certification
criteria and guidelines should be complemented with life cycle assessments that will ensure
that the overall life cycle performance of switchgrass-based bioenergy achieves its intended
outcome.
The market for switchgrass-based bioenergy is likely to evolve substantially over
the next few years, which will necessitate a review of the current standards and protocols.
Future research can verify and adapt the genetic, breeding, establishment, and management
research on switchgrass across agro-ecological regions that focuses on yield, quality, insect
and disease resistance, livestock forage, and its use as a biomass energy crop (Mitchell et
al. 2012). For instance, as the switchgrass stand matures and harvestable dry mater
increases, the carbohydrate and lignin composition changes, reducing the efficiency of
recovering fermentable glucose (Dien et al. 2006). Future research can determine the best
way to manage, harvest, process, transport, convert, and distribute energy from
switchgrass. Future agronomic research can also investigate the response of switchgrass
bioenergy production to nutrients, and how their application rates should be adapted to
factors such as precipitation, chemical and biological attributes of soil, etc. (Mitchell et al.
2008). Research can also devise methods to reduce biomass weight loss, quality loss,
spoilage, and reduce pre-conversion management needs and associated economic and net
energy losses. In addition, it is necessary to adapt the certification standards to various
geographic, sociopolitical, economic contexts. Another important aspect associated with
the implementation and widespread acceptance of a certification standard concerns the
burden of costs and accrual of benefits from certification. The sustainable production of
switchgrass-based bioenergy will not only result in greater societal benefits from an
environmental perspective, but also result in a range of benefits for stakeholders who are
directly and indirectly involved in the production and distribution of the product itself. The
suitability of participatory mechanisms to determine appropriate cost-sharing frameworks
and use of technological inputs to facilitate ease of monitoring and verification are also
important avenues for future research. Finally, the efficiency of certification criteria, and
the marginal benefits arising from certification must be evaluated and validated through
field-based assessments.
In order to maximize the benefits accruing from improved resource allocation and
monitoring using metrics such as net GHG, and energy balance associated with some of
the impact categories, it is necessary to develop easy-to-use tools that are readily
accessible. Outreach programs can work on devising ways to ease the complexity in
developing, managing, and communicating information about switchgrass specialized
criteria indicators to all product users. Furthermore, we can design frameworks that
regulate the industry and maximize the benefits accruing to the industry participants,
without inhibiting growth opportunities whilst ensuring economic and environmental
sustainability. Additionally, future research can assess and enhance the congruence of the
protocol’s criteria and indicators with international trade laws and agreements to reduce
their chance of becoming trade barriers especially if the certification protocols are not
running concurrently among the trading parties in switchgrass-based bioenergy products.
Given the potential for switchgrass based biofuels, future research can devise an effective
operational management strategy and update the criteria and indicators to benefit from new
research and field experience.
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Burli et al. (2016). “Switchgrass-based bioenergy,” BioResources 11(3), 7102-7123. 7118
These criteria, guidelines, and indicators are meant to initiate a broad-based
discussion and guide policy development around creating standards that are easily
implementable and ensure wider acceptance from all stakeholders. Using switchgrass as
an example, we have delineated some of the most crucial aspects of developing a feedstock
specific certification program that can be used a blueprint for other bioenergy feedstocks.
The implementation could involve regulations or voluntary compliance, which can be
subsequently updated based on field experience, local priorities, higher weightage to
indicators that require urgent attention, and site-specific conditions that are in congruence
with the larger objectives of the country’s energy policy.
CONCLUSIONS
1. Biomass certification programs exhibit differences in terms of generalizability, end use
specificity, and applicability across the supply chain, and a one-size-fits-all approach
will not be useful in certifying biofuels produced from different feedstock.
2. Specific guidance documents, such as this paper, have not been developed earlier, and
the methodological aspects highlighted herein can be adapted for other biomass
crops/feedstocks.
3. Integration of switchgrass-specific agronomic recommendations, best management
practices, and research with a more broadly applicable and practical set of criteria and
indicators can provide a robust switchgrass-focused biofuel certification system.
4. The proposed criteria and indicators encompass nine impact categories including land
use, agrochemical application, stand management and harvest, biodiversity, water,
waste management, socioeconomics, air quality, and monitoring. These indicators can
help realize the benefits of switchgrass-based bioenergy while safeguarding from
potential risks.
ACKNOWLEDGMENTS
The authors are grateful for funding from the U. S. Department of Energy award
number DE-P10000031 and the Joint Clean Energy Research and Development Center
(JCERD).
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Article submitted: April 5, 2016; Peer review completed: May 29, 2016; Revised version
received and accepted: June 24, 2016; Published: July 11, 2016.
DOI: 10.15376/biores.11.3.7102-7123
