Running from the Bear: Making Biofuels from Municipal Solid Waste
by Ed Hamrick (Biofuels Digest/Greenworld Fuels) … There are more than two billion tons of MSW produced worldwide every year, with more than 250 million tons per year produced in the USA every year. Disposal of MSW is a thousand year old industry and there’s an efficient and well-established system for collecting it, transporting it and disposing of it. There’s a steady supply of MSW year-round. People pay money for disposing of their MSW. On the surface it looks easy – get a municipality to pay you to take the MSW, make ethanol from it, and pay someone to put what’s left over into their waste dump. It’s not that simple.
The most valuable fraction of MSW is waste paper, comprising up to 40% of MSW in developed countries but only 5% in developing countries. But new Kraft paper pulp costs $800 per ton. Another significant fraction of MSW is food waste, comprising up 20% of the MSW in developed countries and up to 60% in developing countries.
Note that Kraft paper and food waste that haven’t been pulped aren’t good biofuels feedstocks. The wood fibers in paper form a strong mesh of 5 to 50 layers, covered in coatings. Together, this prevents enzymes from accessing the cellulose. Unpulped food waste isn’t a good feedstock either – that’s why we first boil food and then chew it – to form a pulp that enzymes in the body can convert to sugars.
It isn’t difficult to get paper pulp and food pulp from MSW – but it’s very difficult to do this cost-effectively for two reasons: the microorganisms in MSW and the physics of water.
… So the technical challenge of making biofuels from MSW is to make biofuels in populated areas without creating an environmental nuisance.
… Burning the methane/CO2 mixture can produce electricity, but Canada won’t pay subsidies for this electricity and it’s more expensive to produce this electricity than to make electricity from natural gas.
… A solution needs to be located in neighborhoods where the existing transfer stations are located. This minimizes transportation costs and re-uses existing waste collection infrastructure. When the wind blows, the smell can’t annoy the neighbors. It has to be profitable without subsidies, since subsidies can (and do) go away. It can’t emit any toxins into the environment – it has to be something that people won’t object to when it’s located near where their children play. It can’t dump dirty water into the sewers – this is expensive. READ MORE and MORE
