Environmental impacts

WP 4: Environmental impacts



To assess the environmental impacts of handling, storage and field application of fermentates as influenced by the carbon and nutrient pools defined in WP3.



A pilot-scale storage facility will be used to determine GHG and NH3 emission factors for selected fermentates; this will be planned and conducted in collaboration with ATB. As input for improved models of N2O emissions and carbon storage after field application, a mesocosm will be designed. It will allow fermentate to be added to soil at well-defined matric potential. Experiments with fermentates from a large variety of different biomasses, digested

using different retention times and temperatures, will be carried out. Interactions with soil type and water content will be studied. Fluxes of CH4, N2O and CO2 will be measured using gas chromatography, and fluxes of NH3 using an INNOVA photo-acoustic analyser. Sources of N2O will be studied using an LGR N2O isotope analyser. In order to determine the influence of fermentates on soil oxygen content, O2 optodes will be used to study the spatial distribution of oxygen. Long-term incubations measuring CO2 emissions and nitrogen mineralisation will be to assess carbon sequestration and nitrogen leaching via simulations of long-term carbon and nitrogen dynamics using the model Daisy. An existing N2O submodel (Sommer et al. 2004) will be parameterised using experimental results. Estimated GHG emissions and carbon storage will be related to the carbon and nutrient pools determined in WP3 and to the soil processes responsible for carbon and nitrogen transformations using regressio and mechanistic modelling approaches. The influence of digestates and reference materials on soil C storage and GHG emissions at the farm level will be evaluated in collaboration with AAFC who is currently funding research on the integrated influence of dietary manipulation, manure management strategies, and field applications on the net GHG emission and carbon footprint of dairy farms.



The outcome of this WP will be models linking the chemical composition of fermentates to a range of environmental emissions. This can help determine how different starting materials and biogas operational parameters affect the environmental impacts of biogas production and result in improved model parameterisation. The model predictions of environmental emissions will provide input to WP2 and ultimately be used in WP1 for calculation of carbon footprint.


WP3 leader Sander Bruun, Associate professor


University of Copenhagen

Plant and Soil Science Laboratory,

Dept. of Agricultural Sciences,

Faculty of Life Sciences,

Thorvaldsensvej 40,

DK-1871 Frederiksberg C

Phone: +45 3533 3481

Fax: +45 3533 3468

Mobile: +45 2940 6537

e-mail sab@life.ku.dk


PhD projects


Quan Van Nguyen

University of Copenhagen

Department of Plant and Environmental Sciences


The PhD project will focus on the environmental impacts associated with the field application of digestate using a combination of tracer studies and simple modeling. CO2, N2O production potential and others gasesemission (CH4, NH3 and NO) will be examined for varieties of digestates of different feedstocks after field application. Digestates source will be produced from various feedstocks (pig manures, slaughter household wastes, maize silge, and beet root), and differ from retention times. Both short terms and long terms laboratory incubation experiments will be conducted with defferent soil types (C3 and C4).


The overall objectives of the current project are:

•How digestate qualities affect carbon sequestration and greenhouse gases emission after field application to agricultural soil.

•Develop a simple model linking chemical composition of digestate to carbon sequestration and nitrous dioxide production in agricultural soil.





Khagendra Raj Baral

Aarhus University

Department of Agroecology


The overall aim of this PhD study is to determine greenhouse gas emissions for management (storage and field application) of digestates and untreated manure. Further, the work will investigate sources of N2O in digestate/manure-amended soil, and provide input data for a sub-model of N2O emissions from soil. During an international exchange visit to Agriculture & Agrifood Canada, Quebec, experimental data will be analyzed to establish overall GHG balances for digestates and reference materials.


Biogas treatment, by reducing waste dry matter and degradable C, may reduce decomposer activity, including methanogenesis during storage (Sommer et al., 2000) and denitrification processes after field application (Petersen, 1999). Biogas treatment also increases the mineral N content, resulting in a higher concentration of ammoniacal-N compared to untreated slurry which may promote nitrification in the soil. These treatment effects can influence the potentials for emission of methane (CH4) and nitrous oxide (N2O), and hence the greenhouse gas balance, of manure and co-digestates.




Head of the Biochain alliance

Sven Gjedde Sommer

Niels Bohrs Alle 1

DK-5230 Odense M



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