Garbage to gold: Ways to get value from waste (Images)
There's a growing list of methods for getting energy, valuable materials, or compost from the municipal waste stream.
Where there's waste, there's energy and materials. The municipality of Lidkoping, Sweden, began construction last year of a biogas and fertilizer plant that will use waste from the local food industry as its main feedstock. The creation of biogas, mostly methane, happens from naturally occurring microorganisms in enclosed tanks. At this facility, which will cost about $12 million, the biogas is cooled and turned into a liquid. Once the plant is completed, operators expect to handle 60,000 metric tons a year of waste and reduce carbon dioxide emissions by more than 14,000 metric tons annually.
Biogas can be made using wastewater, manure from farms, or municipal solid waste. It can be burned on-site for heat or power, or it can treated and put into natural-gas pipelines. Another possibility is using biogas in a fuel cell to make electricity. This fuel cell is being used in California, where Gills Onions is employing farm waste to make electricity. This same technology is also being used at California wastewater facilities because the state has created incentives for clean-energy technologies.
In the U.S., anaerobic digesters are being used in a number of wastewater treatment plants, such as the Deer Island facility in Boston Harbor. The digesters are the egg-shaped vessels on the left, which convert sewage into biogas that's burned on-site for heat and electricity. The co-generation facility saves the Massachusetts Water Resources Authority (MWRA) $15 million a year in fuel costs. The MWRA has also put up wind turbines and solar panels.
Photo by:Massachusetts Water Resources Authority (MWRA) / Caption by:
Waste to ethanol
A completely different use for municipal solid waste and forestry residue is ethanol. Montreal-based Enerkem is building two commercial-scale plants to take these organic waste products and turn them into ethanol using a process called gasification. The material is fed into a machine like this one and treated with high heat. That breaks most of the material down into a synthetic gas, which can be converted into different chemicals. In August, the company started construction on a facility to treat municipal solid waste in Edmonton, Alberta.
Ze-Gen is another company using gasification to treat waste to get energy, but it's going after a more uniform waste stream: construction and demolition debris. The company has operated a demonstration facility in Massachusetts for more than a year and is seeking to scale up with an industrial company looking for a way to handle waste and produce heat and power on-site. Ze-Gen's gasifier operates at high temperatures, exposing material to heat in a bath of fluid metal.
Another reason to recycle waste is to recuperate valuable materials and prevent runoff into waterways. This machine from Ostara Nutrient Recovery Technologies is called a fluidized bed reactor and is being used by a few wastewater treatment plants in the U.S. The reactor captures the nutrients nitrogen and phosphorus, both of which are vital to agriculture. Ostara recuperates the material and sells it as fertilizers to nurseries and specialty agriculture companies.
Composting outside of individual homes or farms got a boost when municipalities started collecting yard waste. Compost is formed by the natural degradation of organic material by microbes. That compost, which looks like black, fluffy dirt, can be added to soil to return nutrients and fertilize plants. Harvest Power is a start-up company targeting organic waste with both large-scale composting, as seen here, and anaerobic digesters, which create biogas in oxygen-starved vessels. Harvest Power's composting method is designed to work more quickly, cutting composting time from six months for a windrow system to eight weeks.
Waste recycling can be done on-site as well. Vegawatt is a company that's developed an electricity generator tailored specifically for restaurants. The fuel is fryer grease. Pictured here is George Carey, the owner of Finz Seafood & Grill in Dedham, Mass., who's standing next to a Vegawatt Power System.
Garbage hauler Waste Management has invested in a number of smaller companies developing different technologies for converting organic waste to compost and energy. One of those is Terrabon, a company spun out of Texas A&M to commercialize a chemical process for converting biomass into a gasoline replacement. The company has a catalytic process for converting waste into different chemicals, including liquid fuels. In its first tests, it used leftover food and paper from cafeteria dumpsters as a feedstock.
Recycling organic material, or biomass, is still not done at the rate of recycling glass, metal, and plastics. In the 1980s and '90s, many municipalities created recycling programs, leading to the growth of dedicated recycling companies. Here's a bin of automatically separated plastic packaged up and ready for sale to a plastic mill, which will use it for raw material. Household recycling rates in the U.S. are about 30 percent.
About 60 percent of household goods can be recycled, and another 30 percent is organic waste.
One of the fastest sources of waste in the U.S. is electronic waste. This material can and should be recycled as well. Here's a photo from an electronics recycling center in Ontario, Canada, which has a series of machines for shredding and separating e-waste. All the incoming material is recuperated, or older machines are refurbished.