Methane and nitrous oxide emissions from Canadian dairy farms and mitigation options: An updated review

This review examined methane (CH4) and nitrous oxide (N2O) mitigation strategies for Canadian dairy farms. The primary focus was research conducted in Canada and cold climatic regions with similar dairy systems. Meta-analyses were conducted to assess the impact of a given strategy when sufficient data were available. Results indicated that options to reduce enteric CH4 from dairy cows were increasing the dietary starch content and dietary lipid supplementation. Replacing barley or alfalfa silage with corn silage with higher starch content decreased enteric CH4 per unit of milk by 6%. Increasing dietary lipids from 3% to 6% of dry matter (DM) reduced enteric CH4 yield by 9%. Strategies such as nitrate supplementation and 3-nitrooxypropanol additive indicated potential for reducing enteric CH4 by about 30% but require extensive research on toxicology and consumer acceptance. Strategies to reduce emissions from manure are anaerobic digestion, composting, solid-liquid separation, covering slurry storage and flaring CH4, and reducing methanogen inoculum by complete emptying of slurry storage at spring application. These strategies have potential to reduce emissions from manure by up to 50%. An integrated approach of combining strategies through diet and manure management is necessary for significant GHG mitigation and lowering carbon footprint of milk produced in Canada

Tratamento de águas residuárias de suinocultura em reator anaeróbio operado em batelada sequencial Treatment of swine wastewater in anaerobic sequencing batch reactor

Neste estudo avaliou-se o desempenho de um reator anaeróbio operado em batelada sequencial, em escala piloto, com volume total de 280 L, no tratamento de águas residuárias de suinocultura. As cargas orgânicas volumétricas aplicadas no reator foram de 4,42; 5,27; 9,33 e 11,79 g DQOtotal (L d)-1. As eficiências médias de remoção de DQOtotal, sólidos suspensos totais (SST) e sólidos suspensos voláteis (SSV) variaram de 56 a 87%. O nitrogênio total Kjedahl (NTK), fósforo total (P-total) e magnésio (Mg) foram removidos com eficiências médias de 26 a 39%. As produções volumétricas de metano variaram de 0,50 a 0,64 L CH4 (L reator d)-1 e não foram observadas diferenças significativas. As relações sólidos voláteis/sólidos totais (SV/ST) do lodo de tal reator variaram de 0,74 a 0,58. As maiores concentrações médias de nutrientes no lodo do reator foram para o nitrogênio, fósforo, ferro e cálcio, com valores de 30.610 a 64.400, 1.590 a 9.870, 6.180 a 8.700 e 1.180 a 6.760 mg kg-1 base seca, respectivamente.<br>In the present study, we evaluated an anaerobic sequencing batch reactor, in pilot scale and with a total volume of 280 L, for the treatment of swine wastewater. The organic loading rates applied in such reactor were 4.42; 5.27; 9.33 and 11.79 g CODtotal (L d)-1. The average efficiencies of removal of CODtotal total solids suspension (TSS) and volatile suspension solids (VSS) varied from 56 to 87%. The nutrients total Kjedahl nitrogen (TKN), total phosphorus (total P) and Mg were removed with average efficiencies from 26 to 39%. The volumetric methane productions varied from 0.50 to 0.64 L CH4 (L reactor d)-1 and did not present significant differences. The VS/TS relations of the aforementioned reactor's sludge varied from 0.74 to 0.58. The highest mean concentrations of nutrients in the reactor sludge were those of nitrogen, phosphorus, iron and calcium, with values from 30.610 to 64.400, 1.590 to 9.870, 6.180 to 8.700 and 1.180 to 6.760 mg kg-1 base dry, respectively

Influência da relação volumoso: concentrado e do tempo de retenção hidráulica sob a biodigestão anaeróbia de dejetos de bovinos Effects of roughage: concentrate in relation to time of hydraulic retention under anaerobic biodigestion of cattle manure

O objetivo deste trabalho foi avaliar as possíveis alterações existentes na composição e no processo de biodigestão anaeróbia dos dejetos de bovinos em fase de terminação alimentados com diferentes proporções de volumoso: concentrado e com diferentes tempos de retenção hidráulica (TRH). Foram utilizados 24 biodigestores batelada de bancada com 12 litros de capacidade, dos quais 12 foram abastecidos com dejetos de bovinos alimentados com a dieta 1 (60% volumoso:40% concentrado) e dieta 2 (40% volumoso:60% concentrado) e submetidos a 30, 60, 90 e 120 dias de TRH. A eficiência do processo de biodigestão anaeróbia foi avaliada pelas reduções de sólidos totais, sólidos voláteis, fibra em detergente neutro, fibra em detergente ácido, celulose e número mais provável (NMP) de coliformes totais e termotolerantes, além dos potenciais de produção de biogás e metano. Os resultados mostraram que o aumento da proporção de volumoso na dieta levou a menor eficiência do processo, principalmente nos potenciais de produção de biogás e metano que foram em média 13% menor. Com relação ao NMP de coliformes totais e termotolerantes, foram observadas reduções significativas conforme aumentou TRH.<br>The aim of this survey was to evaluate the possible alterations that exist in composition and in anaerobic biodigestion process of cattle manure in phase of slaughter and fed with different proportions of roughage: concentrate and with different times of hydraulic retention (THR). 24 batch digesters of bench with capacity of 12 liters, from which 12 were provided with cattle manure that were fed with diet 1 (60% roughage: 40% concentrate) and diet 2 (40% roughage:60% concentrate) and submitted to 30; 60; 90 and 120 days of TRH were used. The efficiency of anaerobic biodigestion process was evaluated by reductions of total solids, volatile solids; neutral detergent fiber, acid detergent fiber, cellulose and the most probable number (MPN) of total and thermo tolerant coliforms, and production potential of biogas and methane were evaluated. Results showed that the increase of roughage proportion in diet conduced the smallest efficiency in the process, mainly in the production potential of biogas and methane, which were, in average, 13% smaller. Regarding to MPN of total and thermo tolerant coliforms, significative reductions as increased THR were observed