Sasha Hafner

• PhD
• Senior Researcher at Aarhus University

In the rapidly evolving landscape of sustainable energy and resource management, this book is an indispensable resource for students, researchers, and professionals alike. Written by leading experts in the field, it delves into the multifaceted realm of biomass, positioning it as the cornerstone of a non-fossil future. After navigating through the...

Ammonia volatilization from animal slurry applied to agricultural fields reduces nitrogen use efficiency in agriculture and pollutes the environment. This work presents new versions of a model and database focused on this route of N loss. The public ALFAM2 database (https://github.com/AU-BCE-EE/ALFAM2-data) was expanded with ammonia emission and an...

Field-applied liquid animal manure (slurry) is a significant source of ammonia (NH3) emission, which is harmful to the environment and human health. To evaluate mitigation options, reliable emission measurement methods are needed. A new system of dynamic flux chambers (DFCs) with high-temporal-resolution online measurements was developed. The syste...

Greenhouse gas emissions from liquid livestock manure storage significantly contribute to global warming. Accurate farm‐scale models are essential for predicting these emissions and evaluating manure management strategies, but they rely on multiple parameters describing carbon loss dynamics. Surface respiration may significantly influence carbon lo...

Ammonia emission following field application of animal slurry is a significant problem for the environment and human health. Accurate emission measurements are crucial for inventories, research, and mitigation. However, there may be large differences between results obtained with different methods. In this study measurement methods were compared in...

Field applied liquid animal manure (slurry) is a significant source of ammonia (NH3) emission, which is harmful to the environment and human health. To evaluate mitigation options, reliable measurements of effects are needed. A new system of dynamic flux chambers (DFC) with high time resolution online measurements was developed. The system was inve...

Volatilization of ammonia from field-applied animal slurry is a significant problem. Accurate emission measurements are needed for inventories and research, but are not provided by all measurement methods. Wind tunnels may give emission values substantially above or below micrometeorological results, which have been shown to be accurate. This limit...

Emission of greenhouse gases from liquid animal manure (slurry) can be reduced if slurry is treated through anaerobic digestion. The effluent from the reactor (digestate) can be utilized as a nutrient source for crop production if applied in the field. Physical and chemical properties of digestate vary considerably due to large variation in digeste...

Ammonia volatilization from animal slurry applied to fields is a major source of emissions throughout the world. The ALFAM2 model (Hafner et al., 2019) was developed for estimating ammonia emission from this source, and is used for research (Pedersen et al., 2022) and inventories (Hafner et al., 2021). In this contribution we will present recent de...

Poster presented at the RAMIRAN 2023 conference in Cambridge, UK.

Animal slurry (liquid manure) is a significant source of air pollution. Because the biological and chemical processes that drive emission are sensitive to temperature, there is a need for simple tools that can be used to predict the temperature of stored animal slurry for both emissions inventories and research. In this contribution we describe a h...

Poster presented at the EGU 2023 conference in Vienna, Austria.

High ammonia (NH3) and odor emission can occur after land application of liquid animal manure. This study was aimed at evaluating NH3 loss and odor nuisance after field application of cattle manure and how it is affected by two anaerobic digestion strategies: i) digestion of cattle manure alone and ii) digestion with catch crops and dilution by wat...

Reducing methane from livestock slurry is one of the quickest ways to counteract global warming. A straightforward strategy is to reduce slurry retention time inside pig houses by frequent transfer to outside storages, where temperature and therefore microbial activity are lower. We demonstrate three frequent slurry removal strategies in pig houses...

Animal slurry contains plant nutrients such as nitrogen (N) that are essential for crop production. Inorganic slurry N is easily volatilised as ammonia after field application, reducing slurry fertiliser value and causing environmental problems. Ammonia emissions can be reduced by lowering slurry pH, rapid infiltration or incorporation of slurry in...

To assess solid-liquid separation as a technology to reduce ammonia (NH3) emission from storage and field application of animal slurry, it is necessary to consider a possible higher NH3 loss from the solid fraction after application than from raw slurry, as well as losses during storage. A literature review was conducted, and a case study was devel...

Ammonia (NH3) emissions from agriculture have increased by 90% from 1970 to 2005, and agriculture is now the largest source of NH3 to the atmosphere. Calculated national NH3 emissions from agriculture using static emission factors do not reflect regional conditions. We propose, parameterize and test a simple model to calculate emission rates which...

Kinetic information extracted from biochemical methane potential (BMP) tests is often reported but its value is unclear. Inter-laboratory reproducibility provides a useful indication of its value. Here we extracted estimates of the first-order rate constant k from 1259 methane production curves collected in a large inter-laboratory study on BMP in...

To assess solid-liquid separation as a technology to reduce ammonia (NH3) emission from storage and field application of animal slurry, it is necessary to consider a possible higher NH3 loss from the solid fraction after application than from raw slurry, as well as losses during storage. A literature review was conducted, and a case study was devel...

Field application of organic slurries contributes considerably to emissions of ammonia (NH3) which causes sever environmental damage and can result in lower nitrogen (N) fertilizer efficiency. In recent years, field acidification systems have been introduced to reduce such NH3 emissions. However, combined field data on ammonia emissions and N use e...

This document reviews the calculation of emission factors (EFs) for ammonia (NH 3 ) lost from field-applied liquid manure in Denmark and describes the development of new EFs. The original EFs were developed in 2008 (Hansen et al., 2008) using a combination of the ALFAM model presented in 2002 (Søgaard et al., 2002) and fixed emission reductions. Th...

Data analysis is essential in engineering research and practice. But the topic is confusing to many, and inaccurate or completely incorrect conclusions, wasted effort, and miserable students are just too common. This short book provides a concise introduction to data analysis from a very practical perspective. In it I try to explain and demonstrate...

In the biogas industry, feedstock plans are used to estimate methane production and nutrient content in the digestate, however, these predictions do not consider the mineralized nitrogen fraction of the feedstock, which is useful when determining the quality of the digestate. In this study, the artificial fiber bag technique, which is commonly used...

National inventories of methane (CH4) emission from manure management are based on guidelines from the Intergovernmental Panel on Climate Change using country‐specific emission factors. These calculations must be simple and, consequently, the effects of management practices and environmental conditions are only crudely represented in the calculatio...

Liquid manure (slurry) from livestock releases methane (CH4) that contributes significantly to global warming. Existing models for slurry CH4 production—used for mitigation and inventories—include effects of organic matter loading, temperature, and retention time but cannot predict important effects of management, or adequately capture essential te...

The report describes the stability of acidified slurry under Danish conditions and recommended acid doses to reach a pH level of 6.3 ensuring in a 25 percent reduction in ammonia emission during application with trail hoses on fields compared to unacidified slurry Excerpt from the recommendation: With respect to acidification of the slurry duri...

Ammonia (NH3) emissions from land-applied liquid manure (slurry) contribute to nitrogen deposition, acidification, and formation of fine particles in the atmosphere. Optimal management and field application techniques can reduce emission. A reduction in contact area between the slurry and the atmosphere is expected to reduce NH3 emission. The objec...

Nitrous oxide (N2O), ammonia (NH3), and methane (CH4) emissions from the manure management chain of livestock production systems are important contributors to greenhouse gases (GHGs) and NH3 emitted by human activities. Several studies have evaluated manure‐related emissions and associated key variables at regional, national, or continental scales....

Inter-laboratory reproducibility of biomethane potential (BMP) is dismal, with differences in BMP values for the same sample exceeding a factor of two in some cases. A large group of BMP researchers directly addressed this problem during a workshop held in Leysin, Switzerland, in June 2015. The workshop resulted in a new set of guidelines for BMP t...

This is a preprint. Please see final published version instead: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0252881 or https://www.researchgate.net/publication/352311346_A_mechanistic_model_of_methane_emission_from_animal_slurry_with_a_focus_on_microbial_groups Abstract. Livestock slurry releases methane (CH4) that contribute...

This vignette provides an introduction to the ABM package, for simulating anaerobic biodegradation of organic substrates and resulting production of methane and carbon dioxide. For the the package and the latest version, see https://github.com/sashahafner/ABM

The objectives of this study were to: (1) quantify differences in biochemical methane potential (BMP) measured using three measurement methods, including two popular methods (a commercial automated system (AMPTS II) and manual manometric) and one newer method (gravimetric), and (2) assess the importance of the mixing position in the measurement seq...

Biochemical methane potential (BMP) tests used to determine the ultimate methane yield of organic substrates are not sufficiently standardized to ensure reproducibility among laboratories. In this contribution, a standardized BMP protocol was tested in a large inter-laboratory project, and results were used to quantify sources of variability and to...

The impact of storage temperature (4, 22 and 37 °C) and storage time (7, 14 and 21 days) on anaerobic digestion inocula was investigated through specific methanogenic activity assays. Experimental results showed that methanogenic activity decreased over time with storage, regardless of storage temperature. However, the rate at which the methanogeni...

Biochemical methane potential (BMP) tests are commonly applied to evaluate the recoverable amount of methane from a substrate. Standardized protocols require inclusion of a positive control with a known BMP to check the experimental setup and execution, as well as the performance of the inoculum. Only if the BMP of the positive control is within th...

These assignments contain problems to help you practice R skills covered in the book. They are generally available in pdf, R Markdown (*.Rmd), and MS Word formats. If you would like solutions, please contact me.

This zipped archive contains the data files used in the book and the assignments. Download and extract the files to use them. Data are from many different sources, and should not be taken as "real" measurements--in some cases they have been completely made up, and in others they have been modified from the original source.

Field application of liquid manure contributes substantially to atmospheric ammonia. Low emission application methods are commonly used to reduce ammonia transfer to the atmosphere. To document which application method results in lower ammonia volatilization there is a need for high precision measurements to ensure that small differences in total e...

Accurate determination of biochemical methane potential (BMP) is important for both biogas research and practice. However, access to laboratory equipment limits the capacity of small laboratories or biogas plants to conduct reliable BMP assays, especially in low-and middle-income countries. This paper describes the development and validation of a n...

Biochemical methane potential (BMP) tests are routinely conducted in academia and industry to determine the methane potential of a given substrate. Although many guidelines have been proposed to standardize BMP tests, results published in the peer-reviewed literature show that critical flaws in experimental design or execution are still common. The...

A thermal balance modeling framework is developed, based on heat transfer-resistance networks. The heat transfer model accounts for effects of digester- design, location and operation, including effects of solar irradiance, external heating and ambient climate. We demonstrate extendibility of the framework by using the model in dynamic simulations...

This is a workbook for a course on data analysis and graphics in R that I have taught. It might be helpful for new users getting started with R on their own. CONTENTS: 1. Orientation | 2. Introduction to R | 3. Operators and functions | 4. Code, data, and file organization | 5. Getting help | 6. Working with add-on packages | 7. The tidyverse pack...

Accurate determination of biochemical methane potential (BMP) is important for both biogas research and practice. However, access to laboratory equipment (particularly for gas analysis) limits the capacity of small laboratories or biogas plants to conduct reliable BMP assays, particularly in low-and middle-income countries. This manuscript describe...

This work focused on identification and quantification of systematic sources of error in manometric measurement of biochemical methane potential (BMP). Error was determined by comparison to gravimetric measurements and direct measurement of leakage. One out of three types of septa leaked above 1 bar (gauge) head-space pressure, losing 25 to 30% of...

This presentation shows how a simple laboratory scale can be used to improve biochemical methane potential (BMP) measurements through the application of three gravimetric method: gravimetric biogas measurement, leak detection, and a new gas density (GD) BMP method. Each method is briefly described, and experimental results that show advantages and...

This work describes a semi-empirical dynamic model for predicting ammonia volatilization from field-applied slurry. Total volatilization is the sum of first-order transfer from two pools: a "fast" pool representing slurry in direct contact with the atmosphere, and a "slow" one representing fractions less available for emission due to infiltration o...

Ammonia (NH3) emission from animal manure contributes to air pollution and ecosystem degradation, and the loss of reactive nitrogen (N) from agricultural systems. Estimates of NH3 emission are necessary for national inventories and nutrient management, and NH3 emission from field-applied manure has been measured in many studies over the past few de...

Microbial activity during ensiling leads to the production of numerous organic compounds. More than 40 of these compounds are volatile organic compounds (VOC), which readily volatilize when silage is exposed to air. VOC contribute to poor air quality in some areas by participating in atmospheric reactions that produce harmful secondary pollutants,...

Biogas production from organic materials by anaerobic digestion is both a developed technology and an active area of research. In this contribution we describe an R package designed to help standardize biogas research. A web-based application provides access to the main functions. The software can be used to accurately calculate biochemical methane...

Avoiding leaks is essential for accurate measurement of biogas production by batch assays. Here we present a simple method for detecting leaks and correcting results, based on the change in bottle mass during incubation. Three experiments were carried out using pure chemicals, wastewater sludge, and other complex substrates to test and demonstrate...

Avoiding leaks is essential for accurate measurement of biogas production by batch assays. Here we present a simple method for detecting leaks and correcting results, based on the change in bottle mass during incubation. Three experiments were carried out using pure chemicals, wastewater sludge, and other complex substrates to test and demonstrate...

Ammonia emission reduces the reliability and nitrogen (N) fertilizer efficiency of animal manure and mineral fertilizers applied to fields. The loss of ammonia to the atmosphere is frequently compensated for by costly over-application of N fertilizers. New technologies to reduce ammonia emission are regularly developed, and their efficacy needs to...

Combining aerobic and anaerobic digestion in a two-stage system can improve the degradation of wastewater sludge over the use of either technology alone. But use of aerobic digestion as a pre-treatment before anaerobic digestion generally reduces methane production due to loss of substrate through oxidation. An inter-stage configuration may avoid t...

The aim of this study was to investigate thermophilic (55°C) aerobic digestion (TAD) as pre- and inter-stage treatment of sludge anaerobic digestion and to analyse the change in organic matter accessibility and complexity. Pre-treatment decreased methane yield (up to -70%), due to oxidation losses whereas inter-stage treatment slightly improved ove...

Acidification of livestock manure can reduce emission of the greenhouse gases methane (CH4) and nitrous oxide (N2O), as well as ammonia (NH3). We examined the relation between emission of these gases and transformation of organic matter as affected by acidification. Liquid cattle manure was acidified with sulfuric acid to pH 5.5 at a pilot scale (1...

Interfacial mass transfer of \(\hbox {NH}_3\) and \(\hbox {CO}_2\) are important in processes as diverse as \(\hbox {NH}_3\) emission from animal manure and gas scrubbing for removal of carbon dioxide. Predicting transfer rates is complicated by bidirectional interactions between solution pH and emission rates, which may be affected by physical, ch...

A summary of the biogas package and web app OBA

Silage on dairy farms can emit large amounts of volatile organic compounds (VOCs), a precursor in the formation of tropospheric ozone. Because of the challenges associated with direct measurements, process-based modeling is another approach for estimating emissions of air pollutants from sources such as those from dairy farms. A process-based model...

The R package monitoR contains tools for managing an acoustic-monitoring program including survey metadata, template creation and manipulation, automated detection and results management. These tools are scalable for use with small projects as well as larger long-term projects and those with expansive spatial extents. Here, we describe typical work...

Detecting population-scale reactions to climate change and land-use change may require monitoring many sites for many years, a process that is suited for an automated system. We developed and tested monitoR, an R package for long-term, multi-taxa acoustic monitoring programs. We tested monitoR with two northeastern songbird species: black-throated...

Poster presented at AD14 World Congress on Anaerobic Digestion

Theory for predicting biogas production based on substrate composition and degradability is well-developed. But the calculations are tedious and seldom done. The 'biogas' package includes a single function predBg() to make these predictions. This document describes usage of the predBg() function through examples. In a final section, the methods beh...

Ethanol and other volatile organic compounds (VOC) are formed during ensiling, and may contribute to poor air quality and reduce feed intake by animals. Chemical or biological additives may help address these problems by reducing production of VOC during ensiling. The purpose of this study was to evaluate the effect of additives on production of ni...

Ammonia (NH3) emissions from manure constitute a significant loss of fixed nitrogen (N) from agricultural systems and contribute to air pollution and ecosystem degradation. Accurate models of such NH3 emissions will improve our understanding of the factors that control the emissions and allow appropriate mitigation actions to be identified and quan...

The objective of this work was to evaluate the effects of biological and chemical silage additives on the production of volatile organic compounds (VOC; methanol, ethanol, 1-propanol, methyl acetate, and ethyl acetate) within corn silage. Recent work has shown that silage VOC can contribute to poor air quality and reduce feed intake. Silage additiv...

Abstract Text: Silages have the potential to contribute to poor air quality through emission of volatile organic compounds (VOC), especially ethanol. Silage additives may be useful for reducing VOC production, but few studies have evaluated them for this purpose. The objective of this experiment was to test the effects of a biological and a chemi...

Ammonia (NH) emissions vary considerably among farms as influenced by climate and management. Because emission measurement is difficult and expensive, process-based models provide an alternative for estimating whole farm emissions. A model that simulates the processes of NH formation, speciation, aqueous-gas partitioning, and mass transfer was deve...

Ammonia (NH) volatilization from manure in beef cattle feedyards results in loss of agronomically important nitrogen (N) and potentially leads to overfertilization and acidification of aquatic and terrestrial ecosystems. In addition, NH is involved in the formation of atmospheric fine particulate matter (PM), which can affect human health. Process-...

Silage, fermented cattle feed, has recently been identified as a significant source of volatile organic compounds (VOCs) to the atmosphere. A small number of studies have measured VOC emission from silage, but not enough is known about the processes involved to accurately quantify emission rates and identify practices that could reduce emissions. T...

Cumulative emission or gaseous concentrations of ammonia (NH3) are commonly measured by trapping gaseous NH3 in an acidic solution that is later analyzed for total ammonia content. This traditional acid trap method is inexpensive, reliable, and accurate, but it is labor-intensive and inconvenient for high-frequency sampling. This paper describes a...