University of São Paulo, Center of Nuclear Energy in Agriculture, Laboratory of Biogeochemistry, Avenida Centenário, 303, Piracicaba, SP 13416-000, Brazil.
University of São Paulo, "Luiz de Queiroz" College of Agriculture, Department of Soil Science, Avenida Pádua Dias, 11, Piracicaba, SP 13418-900, Brazil.
Sci Total Environ. 2015 Feb 1;505:1018-25. doi: 10.1016/j.scitotenv.2014.10.069. Epub 2014 Nov 10.
As part of an agreement during the COP15, the Brazilian government is fostering several activities intended to mitigate greenhouse gas (GHG) emissions. One of them is the adoption of anaerobic digester (AD) for treating animal manure. Due to a lack of information, we developed a case study in order to evaluate the effect of such initiative for beef cattle feedlots. We considered the net GHG emissions (CH4 and N2O) from the manure generated from 140 beef heifers confined for 90 days in the scope "housing to field application" by including field measurements, literature values, and the offset generated by the AD system through the replacement of conventional sources of nitrogen (N) fertilizer and electricity, respectively. Results showed that direct GHG emissions accounted for 0.14 ± 0.06 kg of carbon dioxide equivalent (CO₂eq) per kg of animal live weight gain (lwg), with ~80% originating from field application, suggesting that this emission does not differ from the conventional manure management (without AD) typically done in Brazil (0.19 ± 0.07 kg of CO₂eq per kg lwg(-1)). However, 2.4 MWh and 658.0 kg of N-manure were estimated to be generated as a consequence of the AD utilization, potentially offsetting 0.13 ± 0.01 kg of CO₂eq kg lwg(-1) or 95% (±45%) of total direct emissions from the manure management. Although, by replacing fossil fuel sources, i.e. diesel oil, this offset could be increased to 169% (±47%). In summary, the AD has the potential to significantly mitigate GHG emissions from manure management in beef cattle feedlots, but the effect is indirect and highly dependent on the source to be replaced. In spite of the promising results, more and continuous field measurements for decreasing uncertainties and improving assumptions are required. Identifying shortcomings would be useful not only for the effectiveness of the Brazilian government, but also for worldwide plans in mitigating GHG emissions from beef production systems.
作为《生物多样性公约》第十五次缔约方大会（COP15）协议的一部分，巴西政府正在推动多项旨在减少温室气体（GHG）排放的活动。其中之一是采用厌氧消化器（AD）处理动物粪便。由于缺乏信息，我们进行了一项案例研究，以评估这一举措对肉牛养殖场的影响。我们考虑了在“圈舍到田间应用”范围内，140 头育肥牛在 90 天内产生的粪便的净温室气体（CH4 和 N2O）排放，包括田间测量、文献值以及 AD 系统通过替代传统氮（N）肥料和电力产生的抵消量。结果表明，直接温室气体排放占动物每增重 1 公斤活重（lwg）的 0.14±0.06 千克二氧化碳当量（CO₂eq），其中约 80%来自田间应用，这表明与巴西通常采用的传统粪便管理（无 AD）没有区别（每增重 1 公斤活重排放 0.19±0.07 千克 CO₂eq）。然而，据估计，由于 AD 的利用，将产生 2.4 兆瓦时和 658.0 千克的 N-粪便，可能会抵消 0.13±0.01 千克 CO₂eq kg lwg(-1)或粪便管理中直接排放的 95%（±45%）。尽管如此，通过替代化石燃料来源，即柴油，这种抵消量可增加到 169%（±47%）。总之，AD 有可能显著减少肉牛养殖场粪便管理中的温室气体排放，但这种影响是间接的，高度依赖于要替代的来源。尽管结果很有希望，但仍需要进行更多和持续的田间测量，以降低不确定性并改进假设。确定缺点不仅对巴西政府的有效性有用，而且对全球范围内减少牛肉生产系统温室气体排放的计划也有用。
