在昨日白宫举行的记者会上，奥巴马表示：“这是一场已持续一段时间的缓慢发酵的危机，不是什么新情况。”
"This is a slow-rolling crisis that has been going on for some time. This is not new, " he said at a White House press conference yesterday.
研究结果从机理上解释了养殖场粪污进行沼气发酵处理时，出现产气量下降甚至不产气的原因。
The results of research explained why gas yield decreased when the faeces of livestock farms was handled with for biogas fermentation.
研究结果从机理上解释了养殖场粪污进行沼气发酵处理时，出现产气量下降甚至不产气的原因。
The results of research explained why gas yield decreased when the faeces of livestock farms was handled with for biogas fermentation.
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