Feature Report: Waste Recovery

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Waste is Worth a Whole Lot of Energy

Waste generated by human activity increased dramatically with the Industrial Revolution in the 19th century and the birth of the consumer society in the 20th century. While it may have a negative connotation, “waste” needn’t be a dirty word. Waste can be reduced right from manufacturing stage, converted into other products and also be a major source of energy. 

Landfill near the Russian Black Sea resort of Sochi. © AFP

Waste comes from a wide variety of sources. The mining, construction, automotive and nuclear industries all produce different forms of waste that need to be treated in highly specific ways. Many other types of waste, such as municipal waste, combustible materials and biodegradables, can be recycled or converted to energy through incinerationTechnique used to convert waste into energy. The waste is burned, producing heat, power or both. or anaerobic fermentation (methanation)Fermentation in the absence of air or free oxygen. .

Waste management is a coordinated process that depends on corporate innovation, government regulation and the environmentally responsible behavior of average citizens.

Recycling

Individual consumers can play a critical role in the recyclingAny waste treatment process that uses materials from identical or similar end-of-life products or manufacturing waste to produce new products. chain by collecting and sorting what they can no longer use, packaging in particular. Many materials — including glass, paper, cardboard, steel from canned goods, aluminum from new forms of packaging and plastic materials of all types — can be reprocessed and reintroduced into the manufacturing circuit to live a second life.

400,000 tons: the amount of agricultural waste processed each year by Germany's largest methanation facility

The European association of plastics manufacturers, PlasticsEurope, has set a clear target to achieve “zero plastics to landfill.” Germany and the Scandinavian countries are close to achieving that goal, but other European countries like France are underperforming. (See Close-Up: "Recycling - Garbage Cans Full of Potential").

Waste Methanation

Organic animal and plant matter from municipal waste, agriculture and agro-industry as well as sewage sludge from wastewater treatment plants can be fermented to produce biogasA product of the methanation (anaerobic digestion) of organic waste..., a mixture of gases mostly consisting of methane (ch4)The main component of natural gas deposits and oil deposit gas caps. Methane is produced naturally by landfills... that can be used to provide heatIn the field of statistical thermodynamics today, heat refers to the transfer of the thermal agitation of the particles making up matter..., powerIn physics, power is the amount of energy supplied by a system per unit time. In simpler terms, power can be viewed as energy output... or automotive fuelFuel is any solid, liquid or gaseous substance or material that can be combined with an oxidant....

By effectively exploiting its waste, Europe could provide 17 million homes with power and 24 million with heat

The advantage of the methanation process is that it can be scaled up or down to meet diverse needs. A small on-farm digester, a system used to produce biogas via this process, has a capacity of around 100 cubic meters. Operating on the other end of the scale, the Penkun plant in Germany has forty 500 kW digesters using 300,000 tons of corn (from stalk to cob), 50,000 tons of grain, 50,000 tons of slurry and 100,000 tons of water every year to generate 160 million kWh of power — enough to supply 40,000 homes with electricityForm of energy resulting from the movement of charged particles (electrons) through a conductor... all year round. At the same time, the facility produces heat through cogenerationThe simultaneous production of both heat (thermal energy) and power... (the combined production of heat and power), of which 30% is used to heat the digesters and 70% to make fertilizer. (See Close-Up: "Methanation - Biogas in our Waste").

Incineration

When they can’t be reused, many types of waste can be incinerated to produce energy in the form of electricity or power. Examples include municipal waste, agricultural and agro-industry waste and industrial waste such as tar and used solvents.

Here again, the pay-offs are considerable. In Denmark, for example, three plants process 3.5 million tons of waste every year to produce 5% of the country’s electricity and 20% of its heat.

Africa is also starting to produce electricity from municipal waste. Morocco inaugurated its first municipal waste-fired power plant in 2010 (See Close-Up: "Incineration - The Heating Power of Refuse").