Dr Mei Bai1, Robert Impraim1, Dr Trevor Coates1, Dr Thomas Flesch2, Dr Raphaël Trouvé3, Dr Hans van Grinsven4, Dr Yun Cao5, Dr Julian Hill6, Professor Deli Chen1
1Faculty Of Veterinary And Agricultural Sciences, The Univeristy Of Melbourne, Parkville, Australia, 2Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB T6G 2R3, Canada, Edmonton, Canada, 3School of Ecosystem and Forest Sciences, Faculty of Science, The University of Melbourne, Richmond, Victoria 3121, Australia, Richamond, Australia, 4PBL Netherlands Environmental Assessment Agency, The Hague, The Netherlands, The Hague, The Netherlands, 5Circular Agriculture Research Centre, Jiangsu Academy of Agricultural Sciences, NanJing 210014, China, Nanjing, China, 6Ternes Agricultural consulting Pty Ltd, Upwey, Victoria 3158, Australia, Upwey, Australia
Emissions of ammonia and greenhouse gases from agricultural systems results in the loss of valuable nitrogen (N), and has negative environmental impacts. Composting manure is a typical management practice on livestock farms, used to increase the content and availability of nutrients. We hypothesize that the addition of lignite, readily available in Australia, can retain N during manure composting. To test our hypothesis, a study was conducted at a commercial feedlot during the summer season. Prior to cattle entering a feedlot pen, we applied 6.48 tonnes of dry lignite to the pen surface, while no lignite was applied to a control pen. After 90 days, the cattle were removed, and manure from each pen was collected to form separate manure windrows, with and without lignite amendments. We quantified gaseous emissions of NH3, nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) from both windrows with a micrometeorological technique using open-path Fourier transform infrared spectroscopy (OP-FTIR). Over the 87 days measurement period, the accumulative gas fluxes showed that the addition of lignite reduced NH3 emissions by 54% during composting, but increased greenhouse gas (GHG) emissions (CO2 equivalent, CO2−e). The N lost as N−NH3 was 9.7% and 24.4% of the total initial N in the lignite and non-lignite windrows, respectively, and the N lost as N−N2O was 0.8% and 0.3% of the total N in the lignite and non-lignite windrows, respectively. To estimate the economic and environmental benefits of reducing gas emissions, we applied a cost-benefit analysis and found that lignite addition to cattle pens cost-effectively improved the nutrient value in final compost product, and could justify trade-off increased GHG emissions.