Anaerobic Digestion: The last frontier for municipal solid waste
Europe could help give an impression of what the U.S. waste disposal industry can become and what future role anaerobic digestion (AD) may play in increasing landfill diversion, producing biogas, nutrient-rich products and compost for municipalities.
The Landfill Directive established by the European Union in 1999 is now firmly established and is on track to reduce the landfilling of biodegradable municipal waste to 35 percent of 1995 levels by 2016. Part of that diversion progress can be attributed to the wide adoption of anaerobic digestion technology to make biogas. Europe now has over 10,000 operating digesters with some communities essentially fossil-fuel-free because of them.
A digester vessel is an air-tight tank that can be of nearly any size or shape. Depending on the type of system employed, with intermittent mixing, digestion time varies depending on the composition of the material being digested, up to a month in some cases. It can be batch-to-batch or continuous process. The technology and economics of the various processes have been established over decades in thousands of installations worldwide, primarily for wastewater and agricultural applications. Now, it looks as though AD is on the verge of breaking through into North American MSW operations.
China’s Green Fence keeps out metals recyclers
Last February, China began more carefully inspecting imports of recyclable metals and other materials to make sure they complied with regulations. The new policy, informally known as Green Fence, went into effect without warning or, at first, any official explanation. It has resulted in added delays, higher costs and in some cases, rejection of recyclables destined for the country.
Recyclables inspectors at Chinese ports reportedly turned back shipments of 68,000 tons in the first 5 months of 2013. It costs more than $2,000 to return a rejected container to the U.S., and the chance of incurring those costs has discouraged recyclers from taking the risk of shipping to China. Partly as a result of Green Fence, Chinese imports of U.S. recyclables fell 11 percent to 3.5 million tons in the first part of 2013, compared with 2012.
For much of the year recyclers from the U.S. and other countries have been trying to figure out the best way to comply with the new inspection regimen. Shippers of post-consumer plastics, paper and automotive shredder output have been especially affected. ...read more