Submitted to: Journal of Renewable and Sustainable Energy
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/28/2011
Publication Date: 7/16/2012
Citation: Cantrell, K.B., Ro, K.S., Szogi, A.A., Vanotti, M.B., Smith, M.C., Hunt, P.G. 2012. Green farming systems for the Southeast USA using manure-to-energy conversion platforms. Journal of Renewable and Sustainable Energy. DOI:10.1063/1.3663846. Interpretive Summary: Future livestock operations in the Southeast USA will need better manure management strategies that generate alternative energy products and safeguard natural resources. In this paper, we review biological and high temperature waste-to-energy treatment options. We also present emerging nutrient recovery technologies that will extract plant-available nitrogen and phosphorous. Anaerobic digestion is the prevalent biological conversion technology that generates biogas and a nutrient-rich slurry. High temperature conversion technologies are more compact in size and capable of handling wet or dry manure feedstocks to produce energy and nutrient-related byproducts. With appropriate downstream processing, the biogases and other energy dense bio-oils can aid farm energy independence. The high temperature processes can also produce a nutrient-dense char that can be used to build soil quality and supply crop nutrients. By better managing manure and its associated wastewater, there is significant opportunity for future livestock farming systems to become profitable and sustainable.
Technical Abstract: Livestock operations in the Southeastern USA are faced with implementing holistic solutions to address effective manure treatment through efficient energy management and safeguarding of supporting natural resources. By integrating waste-to-energy conversion platforms, future green farming systems can ensure sustainable energy supplies. Anaerobic digestion (AD) is the prevalent biochemical platform in the EU and is slowly emerging farm-scale in the USA. Thermochemical conversion (TCC) processes with smaller physical footprints are versatile, capable of handling wet and dry feedstocks to yield multiple byproducts. However, manure feedstock conditioning to lessen the effects of salts, metals, and sulfur is needed along with heat recovery to make these systems energy positive. Both of these processes help achieve different aspects of a green farming system, namely energy generation and nutrient recycle. With appropriate downstream processing, the gases and bio-oils from these systems can aid in farm energy independence. While AD provides a digestate suitable for land application, TCC processes can produce a nutrient-dense biochar that can be used to build soil quality and supply crop nutrients. Any wastewater may be treated with state-of-the-art nitrogen and phosphorous recovery technologies, also allowing for increased water storage when replacing traditional treatment lagoons further promoting water recycle. Through holistic thinking, there is significant opportunity for future livestock farming systems to become profitable and sustainable.