ricardo coronel kauz used to work for the ministry of agriculture.the granulate (from the sewage treatment plant) to fertilize the grass in his pasture. does he think it's a good alternative to chemical fertilizers? >> i think it can soon replace synthetic fertilizer. the world's population is increasing, so it's a step in the right direction. in china it's common to use human excrement and we need to start doing that too. >> switching to the new granulate could save a farmer around 30 tons of chemical fertilizer per year. that is cost effective for the farmer and the sewage treatment plant, since it no longer has to dispose of the sludge. it's good for the environment too. synthetic fertilizers are usually made from fossil fuels. >> the more people use waste products to replace synthetic fertilizers, the more they contribute to the reduction of co2 emissions. >> reducing greenhouse gases and improving water quality has proved a boon to the ecosystem of an entire region. lake managua is connected to the much larger lake nicaragua -- which lies some 5