An evaluation of anaerobic co-digestion implementation on New York State dairy farms using an environmental and economic life-cycle framework
Anaerobic digestion systems on dairy farms in New York State (NYS) rely on gate fees from co-digestion to ensure economic viability.Because gate fees are awarded on a per volume basis,operators are compelled to accept a large waste volume,which increases handling costs and environmental emissions due to larger nutrient loads.To better understand the embedded trade-offs of co-digestion,we performed a combined environmental and economic life-cycle assessment with uncertainty analysis.We used the Anaerobic Digestion Model #1 to simulate the anaerobic digestion process for six potential co-substrates mixed at different co-digestion ratios with dairy manure.Results showed that without gate fees under all co-digestion scenarios,revenue from electricity production and substituted fertilizer could not recover capital costs of the anaerobic digestion system.High co-substrate to manure mixture ratios and high loading rates were more favorable,economically,but led to decreased digester performance (i.e.,decreased specific methane yield and waste stabilization) and increased methane emissions on the farm compared to manure-only digestion.The majority of these on-farm emissions occurred during digestate storage downstream of the digester.Yet,total life-cycle emissions,which include emissions occurring outside the farm boundary,were lower for most co-digestion scenarios compared to manure-only digestion due to greater electricity savings and fertilizer offsets.Gate fees were the main driver behind economic profitability and this revenue greatly outweighed the economic effects induced by co-substrate composition and digester performance.Consequently,low organic strength rather than energy-rich co-substrates are more economically desirable.Our results suggest that the main environmental benefits associated with anaerobic digestion: energy offsets,waste stabilization,and on-farm emission mitigation,are currently undervalued in NYS.We recommend three policy measures aiming to incentivize environmentally favorable co-digestion management practices.
Biogas co-digestion dairy economic life-cycle assessment farm emissions
J.G.Usack L.Gerber Van Doren R.Posmanik R.A.Labatut J.W.Tester L.T.Angenent
Department of Biological and Environmental Engineering, University of Tuebingen, Canada;Center for A Department of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, 14853, USA Department of Hydraulic and Environmental Eng., Pontifical Catholic University of Chile, Santiago, C
国际会议
The 15th IWA World Conference on Anaerobic Digestion( 第15届IWA世界厌氧大会)
北京
英文
803-806
2017-10-17（万方平台首次上网日期，不代表论文的发表时间）