Water hyacinth (Eichhornia crassipes), an aquatic plant native to South America, first appeared in countries in Africa in the early 1900s. Scientists there called it the 'world's worst aquatic weed', after it spread from the southernmost tip of Africa in the early 1900s and started obstructing major dams and rivers.

水马齿苋（Eichhornia crassipes）是一种原产于南美洲的水生植物，20世纪初首次出现在非洲国家。当地科学家称其为“世界上最严重的水生杂草”，因为它在19世纪末从非洲最南端传播开来，开始堵塞主要的水坝和河流。

In east Africa the plant arrived with Belgian colonists in Rwanda, who liked the look of its glossy leaves and delicate purple flowers floating in their ponds. But by the 1980s, it had 'escaped' out of the country via the Kagera river and made its way downstream to Lake Victoria. There, with no natural predators and perfect temperature conditions, the plant began spreading in the open water, blocking fishing routes and providing a new habitat for disease-carrying mosquitoes.

在东非，这种植物最初由比利时殖民者带入卢旺达，他们喜欢它那光泽的叶片和漂浮在池塘中的精致紫色花朵。但到了20世纪80年代，它通过卡盖拉河“逃逸”出国，并顺流而下进入维多利亚湖。在那里，由于没有天敌且水温适宜，这种植物开始在开阔水域迅速蔓延，阻塞了渔获路线，同时也为传播疾病的蚊子提供了新的栖息地。

For the women who smoke fish from the lake to sell it has meant declining income, as the boats that once brought the fish to shore by the hundreds struggle to navigate through the mass of plants. But water hyacinth isn't their only headache. In order to smoke the fish that they buy, they must gather huge quantities of firewood, sometimes walking as far as 10km each way to collect enough to complete their work. And each day as they cook, they breathe in the thick, grey smoke. About three out of four families in Kenya depend on wood or charcoal to cook their daily meals, and the rate is even higher in rural areas, Kenya's latest demographic and health survey shows.Using solid fuels like these for cooking increases indoor pollution. The World Health Organization estimates that about 14,300 Kenyans die annually as a result of indoor air pollution - most of which is caused by cooking and heating sources.

对于这些女性来说，将湖中的鱼烟熏后出售意味着收入下降，因为曾经成百上千条船只将鱼运上岸，如今却难以穿过密布的植物群。但水葫芦并非她们唯一的烦恼。为了烟熏所购的鱼，她们必须大量收集柴火，有时单程步行长达10公里，只为完成这项工作。每天烹饪时，她们吸入着浓重的灰色烟雾。肯尼亚最新的人口与健康调查显示，约四分之三的家庭依靠木柴或木炭来烹煮日常饭菜，而在农村地区这一比例更高。使用这类固体燃料进行烹饪会加剧室内空气污染。世界卫生组织估计，每年约有1.43万人因室内空气污染死亡，其中大多数是由烹饪和取暖设备造成的。

Some years ago, on the shores of Lake Victoria, huge piles of water hyacinth that villagers had taken out of the water in an attempt to clear it were a common sight. But buried in those decaying waxy leaves was a renewable energy gold mine. It turns out the floating plant isn't just good at spreading - its foliage also contains a high ratio of carbon to nitrogen. It's a magic combination that has captivated researchers' imaginations since as early as the 1980s when, across the world, they began to explore its potential as a biofuel. Just about 4kg of the dried plant would be enough to cater for a large family's daily energy needs, early research predicted.

几年前，在维多利亚湖的岸边，村民们为清理水体而捞出的大量睡莲曾是常见的景象。然而，这些腐烂的蜡质叶片中却蕴藏着一种可再生能源的宝藏。原来这种漂浮植物不仅生长迅速，其叶片还含有较高的碳氮比。这种神奇组合自20世纪80年代起便吸引了研究人员的关注，当时全球开始探索它作为生物燃料的潜力。早期研究预测，仅约4公斤干制植物就足以满足一个大家庭每日的能量需求。

In 2014, Nigerian academics announced they had got better yields of biofuel gas when they mixed the plant with chicken manure. A few years later, Kenyan scientists confirmed what their Nigerian peers and others had already found: manure worked to improve the process of converting the weed into gas.

2014年，尼日利亚的学者宣布，当他们将这种植物与鸡粪混合时，生物燃料气体的产量有所提高。几年后，肯尼亚科学家证实了尼日利亚同行及其他研究者早已发现的事实：粪便有助于改善将杂草转化为气体的过程。

In 2018, the technology came to a village on the shore of Lake Victoria, called Dunga.The project promised a two-for-one solution to the dual menaces of the water hyacinth and dependence on firewood. The community received a pair of donated biogas digesters - machines that would transform a mix of water hyacinth and cow dung into biogas for cooking.

2018年，这项技术来到维多利亚湖畔的一个名为敦加的村庄。该项目承诺提供一种一举两得的解决方案，既能应对水葫芦带来的威胁，又能摆脱对柴火的依赖。当地社区收到了两台捐赠的沼气发酵器——这些机器可将水葫芦和牛粪混合物转化为可用于烹饪的沼气。

The digesters work a bit like a stomach. The mixture goes in one end - think of it as a mouth - and over the next 20 to 30 days, it goes through a fermentation process and breaks down, giving off gas that comes out the other end. From there, the clean- burning gas is passed through pipes to the point of use, just like traditional domestic gas. In Dunga, the machines produce enough gas to serve about 60% of the village's population. It is used in domestic stoves and for other household tasks such as purifying water and incubating chicks.

消化器的工作原理类似于胃。混合物从一端进入，可以想象成嘴巴，然后在接下来的20到30天内经历发酵过程，分解产生气体，通过另一端排出。随后，这种清洁燃烧的气体通过管道输送到使用地点，就像传统家用燃气一样。在敦加，这些机器产生的气体足以满足约60%村庄人口的需求，用于家庭炉灶以及水净化、孵化小鸡等其他家务用途。

The project is testing whether biogas can provide an effective alternative to firewood and charcoal in rural Kenyan communities. Results indicate that the programme seems to be working. The women who smoke the lake fish are already getting sick less often.Besides, they don't have to devote a lot of time every day to gathering firewood, which is a great relief. As a result, they're able to make more money for their families from other enterprises.

该项目正在测试沼气是否能成为肯尼亚农村社区替代柴火和木炭的有效选择。结果显示，该计划似乎正在奏效。那些捕捞湖鱼的妇女们生病的频率明显降低了。此外，她们不再需要每天花费大量时间去采集柴火，这带来了极大的便利。因此，她们能够从其他事业中为家庭赚取更多收入。

Kanyiva Muindi is an epidemiologist and air pollution research fellow at the African Population and Health Research Centre in Nairobi. She says families who switch to the smokeless cooking method could expect fewer respiratory diseases. Women, young girls and children are particularly vulnerable because they are the ones who cook in the kitchen or outside over fires.

卡尼瓦·穆因迪是内罗毕非洲人口与健康研究中心的流行病学家和空气污染研究研究员。她表示，采用无烟烹饪方式的家庭可能会减少呼吸道疾病的发生。女性、年轻女孩和儿童尤其脆弱，因为她们通常在厨房或户外用火做饭。

How much better the biogas stoves will be for the community's health still needs more research, says Dominic Kahumbu Wanjihia, Biogas International's chief executive. But unless the price of the machines drops, it's pretty clear that most communities will never be able to afford any, since they sell for about $750.

生物沼气炉对社区健康将带来多大益处，仍需进一步研究，生物沼气国际首席执行官多米尼克·卡洪布·万吉希亚表示。但除非机器价格下降，否则显然大多数社区永远无法负担得起，因为这些设备售价约为750美元。

Kanyiva says affordability is a challenge worth addressing, given the huge health and environmental dangers posed by 'dirty' fuels such as wood, charcoal and kerosene. If biogas could become affordable on a large scale, she says it 'would be life-changing for millions on the African continent and beyond'.

卡尼瓦表示，鉴于木材、木炭和煤油等“脏燃料”带来的巨大健康和环境危害，可负担性是一个值得解决的挑战。她认为，如果沼气能够大规模实现价格合理，那将“对非洲大陆乃至更广泛地区数以百万计的人们带来改变”。