Methane production in low-cost, unheated, plug-flow digesters treating swine manure and used cooking grease.
A co-digestion investigation was conducted using small-scale digesters in Costa Rica to optimize their ability to treat animal wastewater and produce renewable energy. Increases in methane production were quantified when swine manure was co-digested with used cooking grease in plug-flow digesters that operated at ambient temperate without mixing. The co-digestion experiments were conducted on 12 field-scale digesters (250 L each) using three replications of four treatment groups: the control (T0), which contained only swine manure and no waste oil, and T2.5, T5, and T10, which contained 2.5%, 5%, and 10% used cooking grease (by volume) combined with swine manure. The T2.5 treatment had the greatest methane (CH(4)) production (45 L/day), a 124% increase from the control, with a total biogas production of 67.3 L/day and 66.9% CH(4) in the produced biogas. Increasing the grease concentration beyond T2.5 produced biogas with a lower percentage of CH(4), and thus, did not result in any additional benefits. A batch study showed that methane production could be sustained for three months in digesters that co-digested swine manure and used cooking grease without daily inputs. The investigation proved that adding small amounts of grease to the influent is a simple way to double energy production without affecting other digester benefits.
Lansing
Stephanie
S
Department of Environmental Science and Technology, University of Maryland, 1445 Animal Sci./Ag. Eng. Bldg., College Park, MD 20742-2315, USA. slansing@umd.edu
Martin
Jay F
JF
Botero
Raúl Botero
RB
da Silva
Tatiana Nogueira
TN
da Silva
Ederson Dias
ED
D000818:Animals; D056804:Biofuels / Q000032:analysis*; D003296:Cooking; D006358:Hot Temperature; D006862:Hydrogen Sulfide / Q000032:analysis; D008372:Manure / Q000032:analysis*; D008697:Methane / Q000096:biosynthesis*; D009821:Oils / Q000737:chemistry*; D012621:Seasons; D012722:Sewage; D013552:Swine; D013997:Time Factors; D014865:Waste Disposal, Fluid / Q000191:economics* / Q000295:instrumentation*
D056804:Biofuels; D008372:Manure; D009821:Oils; D012722:Sewage; D008697:Methane; D006862:Hydrogen Sulfide