GHG emissions from slurry and digestates during storage and after field application

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Documents

Khagendra Raj Baral, Quan Van Nguyen, Søren O. Petersen, Sander Bruun

The BioChain project focuses on value chains for biogas production in Denmark. Biogas production is based on liquid manure (slurry) from agriculture and other biomasses to increase the energy yield. To a great extent the digestates are recycled to agricultural lands as a valuable fertilizer, but environmental impacts, such as greenhouse gas (GHG) emissions, during storage and after field application should take into account. Mainly, methane (CH4) is produced during storage and nitrous oxide (N2O) after field application. Currently, direct (CH4, N2O) and indirect (NH3) GHG emissions during storage are determined in a pilot-scale study with digested materials from Maabjerg Bioenergy and Fredericia Wastewater Treatment Facility, using untreated cattle and pig slurry as reference. These and other results will be used to model the effect of temperature and pre-treatment on CH4 emissions. The composition of volatile solids (VS) is critical for predicting GHG emissions and the effect of biogas treatment. Volatile solids may be considered to have an easily degradable VS (VSd) and a slowly degradable VS (VSnd) fraction. A new approach to estimate VSd was investigated using the short-term evolution of CO2-C from slurry/digestates when incubated in soil under aerobic conditions. The experimental treatments included untreated pig slurry, sugarbeet root pulp, or pig slurry co-digested with 0%, 12.5%, 25% or 90% sugarbeet pulp. Proportions of VSd ranged from 25 to 67%. Methane emissions during storage will be modelled using this information (Sommer et al., 2004). Similarly, short-term N2O emissions from field applied slurry/digestates are predicted using a N2O sub-model first presented by Sommer et al. (2004). The model considers N2O emission to be a function of VS in slurry or digestate, reactive slurry nitrogen (N), and soil water potential (). Short-term N2O emissions, expressed as percentage of total N applied, ranged from 0.24 to 1.4%.

Overall, first results indicate that co-digestion of pig slurry and sugar beet pulp may reduce GHG emissions during storage and after field application. The extent and duration of anaerobic conditions in soil-manure environments depends on VS availability.Under control setup, oxygen optodes are used to investigate O2 depletion from slurry applied soils.
Original languageEnglish
Publication date23 Nov 2014
Publication statusPublished - 23 Nov 2014
EventEnergy and Environment for the Future - Eigtveds Pakhus, Copenhagen, Denmark
Duration: 24 Nov 201425 Nov 2014
http://www.biopress.dk/events/energy-and-environment-for-the-future-1

Conference

ConferenceEnergy and Environment for the Future
LocationEigtveds Pakhus
CountryDenmark
CityCopenhagen
Period24/11/201425/11/2014
Internet address

    Research areas

  • Faculty of Science - Biochain, Biogas optimization, GHG emissions, C sequestration, N2O emission

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