Nutrient pollution and greenhouse gas emissions related to crop agriculture and confined animal feeding operations (CAFOs) in the US have changed substantially in recent years, in amounts and forms. This review is intended to provide a broad view of how nutrient inputs—from fertilizer and CAFOs—as well as atmospheric NH3 and greenhouse gas emissions, are changing regionally within the US and how these changes compare with nutrient inputs from human wastewater. Use of commercial nitrogen (N) fertilizer in the US, which now exceeds 12,000,000 metric tonnes (MT) continues to increase, at a rate of 60,000 MT per year, while that of phosphorus (P) has remained nearly constant over the past decade at around 1,800,000 MT. The number of CAFOs in the US has increased nearly 10% since 2012, driven largely by a near 13% increase in hog production. The annualized inventory of cattle, dairy cows, hogs, broiler chickens and turkeys is approximately 8.7 billion, but CAFOs are highly regionally concentrated by animal sector. Country-wide, N applied by fertilizer is about threefold greater than manure N inputs, but for P these inputs are more comparable. Total manure inputs now exceed 4,000,000 MT as N and 1,400,000 MT as P. For both N and P, inputs and proportions vary widely by US region. The waste from hog and dairy operations is mainly held in open lagoons that contribute to NH3 and greenhouse gas (as CH4 and N2O) emissions. Emissions of NH3 from animal waste in 2019 were estimated at > 4,500,000 MT. Emissions of CH4 from manure management increased 66% from 1990 to 2017 (that from dairy increased 134%, cattle 9.6%, hogs 29% and poultry 3%), while those of N2O increased 34% over the same time period (dairy 15%, cattle 46%, hogs 58%, and poultry 14%). Waste from CAFOs contribute substantially to nutrient pollution when spread on fields, often at higher N and P application rates than those of commercial fertilizer. Managing the runoff associated with fertilizer use has improved with best management practices, but reducing the growing waste from CAFO operations is essential if eutrophication and its effects on fresh and marine waters–namely hypoxia and harmful algal blooms (HABs)—are to be reduced.

中文翻译：

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从生猪到有害细菌：美国工业化养殖对氮磷和温室气体污染的影响


近年来，美国与农作物农业和封闭式动物饲养场 (CAFO) 相关的养分污染和温室气体排放在数量和形式上都发生了巨大变化。本综述旨在提供一个广泛的视角，了解来自化肥和 CAFO 的养分输入以及大气中的 NH3 和温室气体排放在美国境内的区域变化，以及这些变化与人类废水中的养分输入相比如何。美国商业氮 (N) 肥料的使用量目前已超过 12,000,000 公吨 (MT)，并以每年 60,000 公吨的速度持续增加，而磷 (P) 的使用量在过去十年中几乎保持不变，为每年 60,000 公吨。约 1,800,000 公吨。自 2012 年以来，美国 CAFO 的数量增加了近 10%，这主要是由于生猪产量增加了近 13%。牛、奶牛、生猪、肉鸡和火鸡的年存栏量约为 87 亿头，但 CAFO 的畜牧业在区域上高度集中。在全国范围内，化肥施用的氮大约是粪肥氮投入的三倍，但对于磷而言，这些投入更具可比性。目前，N 粪肥输入总量超过 4,000,000 公吨，P 粪肥输入总量超过 1,400,000 公吨。对于 N 和 P，输入量和比例因美国地区而异。生猪和奶制品养殖场产生的废物主要存放在开放式泻湖中，这会导致氨和温室气体（如甲烷和一氧化二氮）的排放。 2019 年动物粪便中的 NH3 排放量估计为 > 4,500,000 公吨。 1990年至2017年，粪便管理产生的CH4排放量增加了66%（乳制品增加134%，牛增加9.6%，生猪增加29%，家禽增加3%），而同期N2O排放增加34%（乳制品增加15%） ，牛 46%，生猪 58%，家禽 14%）。 CAFO 产生的废物在散布到田间时会严重造成养分污染，且氮和磷的施用率通常高于商业化肥。通过最佳管理实践，与化肥使用相关的径流管理得到了改善，但如果要减少富营养化及其对淡水和海水的影响（即缺氧和有害藻华 (HAB)），减少 CAFO 运营中不断增加的废物至关重要。