Why worms (and microbes) are catching on as a manure pollution solution
Why worms (and microbes) are catching on as a manure pollution solution
为什么蚯蚓（和微生物）正成为解决粪便污染的新方案
EXECUTIVE SUMMARY Anthony Agueda, a third-generation California dairy farmer, pulls a rake through a bed of dark, wet wood chips on his family’s land in Hickman, a tiny town in the state’s agricultural heartland. He reaches down with both hands and pulls up a clump of muck, turning it over to reveal a half-dozen squirming red earthworms. There are likely hundreds of thousands more wriggling just under the surface of the three-foot mound of wood and crushed river rock before us, which stretches across the equivalent of six football fields.
执行摘要 安东尼·阿格达（Anthony Agueda）是加利福尼亚州第三代奶农。在位于该州农业腹地希克曼（Hickman）镇的家族土地上，他正用耙子翻动着一片潮湿阴暗的木屑床。他俯下身，双手抓起一团污泥，翻开一看，里面有半打正在蠕动的红蚯蚓。在我们面前，这堆三英尺高、占地面积相当于六个足球场的木屑和碎河石堆下，很可能还有成千上万条蚯蚓在蠕动。
These natural materials form a biofilter that may dramatically cut the methane, nitrous oxide, and water pollution generated by the massive amounts of manure that hundreds of Holstein cows produce each day. Agueda’s family business, the Alberto Dairy, was one of the first cattle operations in California to adopt this approach to manure treatment, developed and patented by the Chilean company BioFiltro. Eight more of these so-called vermifiltration systems are already operating on US dairies, according to the company, while another 16 are under construction or set to be next year, nearly all of them in California.
这些天然材料构成了一个生物过滤器，可以显著减少数百头荷斯坦奶牛每天产生的大量粪便所带来的甲烷、氧化亚氮和水污染。阿格达家族经营的阿尔贝托奶牛场（Alberto Dairy）是加州首批采用这种粪便处理方法的养牛场之一，该技术由智利公司 BioFiltro 开发并拥有专利。据该公司称，目前美国已有八家奶牛场在使用这种所谓的“蚯蚓过滤系统”（vermifiltration），另有 16 套系统正在建设中或计划于明年投入使用，其中几乎全部位于加州。
Vermifiltration is just one of a variety of methods that farmers, companies, and scientists are employing to drive down manure pollution as the livestock industry faces growing pressure to address the environmental harms from one of the smelliest parts of the business. California, easily the nation’s largest milk producer, has established a handful of programs to promote their adoption, including one initiative that has funneled more than a billion dollars to farms. Researchers stress that much more work needs to be done to determine the most effective approaches, the trade-offs between them, and their success over the long term, under actual farm conditions.
随着畜牧业面临越来越大的压力，需要解决其业务中最令人头疼的污染问题，蚯蚓过滤法只是农民、企业和科学家们用来减少粪便污染的多种方法之一。作为全美最大的牛奶生产州，加州已经建立了一系列项目来推广这些技术的应用，其中一项计划已向农场投入了超过十亿美元的资金。研究人员强调，仍需开展大量工作，以确定最有效的方法、各种方法之间的权衡，以及它们在实际农场环境下的长期成效。
Agueda says that he and his family recognized the need to adopt new practices as environmental rules tightened. They were drawn to vermifiltration because it’s simple and relatively cheap compared with other, higher-tech options. “California daily farmers are constantly facing more and more regulation,” says Agueda, standing alongside one of the farm’s free-stall barns. “This makes me excited, because it shows how we are part of the solution.”
阿格达表示，随着环境法规的日益严格，他和家人意识到必须采取新的做法。他们之所以选择蚯蚓过滤法，是因为与其他高科技方案相比，它既简单又相对便宜。“加州的奶农正不断面临越来越多的监管，”阿格达站在农场的一间散栏式牛舍旁说道，“这让我感到兴奋，因为它表明我们也是解决方案的一部分。”
The growing manure problem Manure is responsible for a significant portion of the climate pollution from livestock operations. The World Resources Institute estimates that manure management on dairy and swine farms accounts for 1.6% of the US’s greenhouse-gas emissions. Globally, manure storage and processing makes up about 10% of the livestock industry’s contributions to climate change. “Farms have become larger in the past two decades or so, so there’s much more manure—and that has to be stored somewhere,” says Swati Hegde, the organization’s global manager of agricultural methane.
日益严重的粪便问题 粪便在畜牧业产生的气候污染中占很大比例。世界资源研究所估计，奶牛场和养猪场的粪便管理占美国温室气体排放量的 1.6%。在全球范围内，粪便的储存和处理约占畜牧业对气候变化影响的 10%。“在过去二十年左右的时间里，农场规模变得越来越大，因此产生的粪便也更多——这些粪便必须储存在某个地方，”该组织全球农业甲烷经理斯瓦蒂·赫格（Swati Hegde）说。
Typically, cattle and swine farms spray manure into lagoons or tanks, creating a foul-smelling, low-oxygen slurry in which microorganisms known as methanogens thrive. They gobble up hydrogen, carbon dioxide, and other compounds and produce methane as a by-product. Other microbes in the mix produce smaller amounts of nitrous oxide. Both are particularly potent greenhouse gases, with as much as 30 to nearly 275 times the warming power of carbon dioxide, respectively, over a century.
通常，牛场和猪场会将粪便喷入泻湖或储罐中，形成一种气味难闻、低氧的泥浆，而被称为“产甲烷菌”的微生物就在其中大量繁殖。它们吞噬氢气、二氧化碳和其他化合物，并产生甲烷作为副产品。混合物中的其他微生物则会产生少量的氧化亚氮。这两种气体都是效力极强的温室气体，在百年尺度上，其增温能力分别是二氧化碳的 30 倍到近 275 倍。
The slurry is often spread onto fields to add nutrients to the soil. When it’s done excessively or improperly, this part of the practice can pollute soil or groundwater with drug residues, pathogens like salmonella and E. coli, and nitrates. Nitrates that leach into drinking water have been linked to a variety of human health risks. And those that flow into rivers, lakes, and coastal waters can spawn algae blooms that poison fish, block sunlight, suck up oxygen, or form large coastal dead zones devoid of marine life.
这种泥浆通常会被喷洒到田间，为土壤增加养分。如果操作过度或不当，这一做法可能会导致药物残留、沙门氏菌和大肠杆菌等病原体以及硝酸盐污染土壤或地下水。渗入饮用水中的硝酸盐已与多种人类健康风险挂钩。而流入河流、湖泊和沿海水域的硝酸盐则会引发藻类爆发，导致鱼类中毒、阻挡阳光、耗尽氧气，或形成大面积缺乏海洋生物的沿海“死亡区”。
Policy drivers A number of regions, nations, and states have passed regulations or offered subsidies designed to limit the pollution from livestock manure, but so far, most of the major initiatives have focused on water contamination rather than greenhouse-gas emissions. The European Union, for instance, restricts the amount of manure that farmers can apply to fields and requires member nations to monitor nitrate levels in ground and surface water. The US’s Clean Water Act requires large livestock operations to obtain permits and develop manure management plans that limit pollution.
政策驱动 许多地区、国家和州已经通过了法规或提供了补贴，旨在限制畜牧粪便造成的污染，但到目前为止，大多数主要举措都集中在水污染而非温室气体排放上。例如，欧盟限制了农民在田间施用粪便的数量，并要求成员国监测地下水和地表水中的硝酸盐水平。美国的《清洁水法》要求大型畜牧企业必须获得许可，并制定限制污染的粪便管理计划。
But California has arguably done the most to use government policy specifically to drive down the methane emissions from livestock. The dairy industry accounts for about 45% of the state’s pollution from the potent greenhouse gas, and more than half of that comes from manure, according to the government’s estimates. In 2016, the state enacted a law that requires dairies, landfills, and other businesses to cut methane emissions 40% below 2013 levels by 2030, as part of a broader effort to reduce pollution from powerful but short-lived greenhouse gases.
但可以说，加州在利用政府政策专门降低畜牧业甲烷排放方面做得最多。据政府估计，加州约 45% 的甲烷排放来自奶牛业，其中超过一半来自粪便。2016 年，该州颁布了一项法律，要求奶牛场、垃圾填埋场和其他企业在 2030 年前将甲烷排放量削减至 2013 年水平的 40% 以下，这是减少强效但短寿命温室气体污染的更广泛努力的一部分。
The measure directed the California Air Resources Board, the state’s main climate regulatory agency, to set up various incentive programs to encourage these industries to shift to cleaner practices. “In terms of bang for your buck, short-term benefits, methane can go a long way toward reaching climate goals,” says Tawny Mata, director of California’s Office of Agricultural Resilience and Sustainability. Between these various programs—and falling livestock numbers in the state—the dairy sector is on track to reduce annual methane emissions by the equivalent of 5 million metric tons of carbon dioxide by 2030, the state estimates. That would still fall about 4 million tons short of the target under the 2016 law.
该措施指示加州的主要气候监管机构——加州空气资源委员会（California Air Resources Board）——设立各种激励计划，鼓励这些行业转向更清洁的生产方式。“从性价比和短期效益来看，减少甲烷排放对于实现气候目标大有裨益，”加州农业韧性与可持续发展办公室主任托尼·马塔（Tawny Mata）表示。加州估计，通过这些项目以及该州牲畜数量的下降，奶牛业有望在 2030 年前将年度甲烷排放量减少相当于 500 万公吨二氧化碳的水平。但这仍比 2016 年法律设定的目标少了约 400 万吨。