The goals agreed to at the 21st United Nations Climate Change Conference (COP21) in 2015, collaboratively known as the Paris Agreement, are an ambitious call for action: The aim is to keep global warming below 2 degrees Celsius (3.6 degrees Fahrenheit).
For this to happen, the emission of greenhouse gases will have to be completely halted between 2045 and 2060, and the production of carbon dioxide (CO2) reduced to levels that can be absorbed by natural photosynthesis. According to current studies, this will entail stopping the burning of fossil fuels entirely from 2040 and switching completely to renewable sources of energy.
However, it is not just industry and transportation that are responsible for imbalances in the carbon cycle. Landfill sites currently account for around 8 percent of greenhouse gas emissions. Amid rising population numbers and the resultant volumes of waste, this number also is set to increase. Experts expect waste volumes to reach 2.4 billion tons by 2025, producing 1.3 billion tons of CO2 equivalent greenhouse gases.
Consequently, sustainable waste management has a bearing on the world’s climate. Companies such as mine, Zurich-based Hitachi Zosen Inova (HZI), say they can address this issue with products comprising a range of energy-from-waste (EFW) and power-to-gas (PTG) technologies.
ENERGY FROM NONRECYCLABLE WASTE
In many parts of Europe, recyclables are collected separately, with the residual waste then processed in EFW plants. This trend is becoming increasingly more attractive in the U.S. and Canada because it is designed to offer a range of advantages, such as reducing or completely eradicating the need for landfill, cutting greenhouse gases and protecting the natural habitat from contamination and pollution.
Grate incineration, with flue gas treatment and material recovery technologies, is designed to ensure the smooth running of industrial, manufacturing and municipal plants using conversion technology, which is subsequently fed into the grid as base-load power to supply households and commercial facilities.
Modern EFW plants can deliver enough heat from a ton of waste to replace approximately 63 gallons of heating oil, for example, or generate 800 kilowatt hours (kWh) of electricity, enough to supply an average household in the U.S. or Canada with electricity for approximately one month, based on a total annual consumption of approximately 10,000 kWh per year.
A municipal EFW plant in Peden, Switzerland, employs combustion technology and dry flue gas cleaning. The HZI plant processes 220,000 tons of municipal nonrecyclable waste annually, supplying 155 gigawatt hours (GWh) of electricity for 38,000 households and 350 GWh of process steam for commercial use.
Biogas plants can round out the energy generation portfolio. Kompogas plants, which operate in several hundred municipalities worldwide, convert green waste and biowaste into compost, fertilizer and biomethane, a storable fuel that can be used on demand.
Biomethane can replace fossil fuels when made available as compressed natural gas for vehicles. One ton of green waste produces the equivalent of about 17 gallons of fuel, enough to power a vehicle for some 420 miles. Or, it can generate 220 kWh of power, enough to supply approximately 27 percent of the electrical energy needs of an average North American household for one month.
Variable energy resources, such as solar and wind, often generate more power than is needed. Technologies such as HZI’s Etogas can harness these peaks in renewable energy to produce synthetic natural gas from surplus energy. This synthetic natural gas is storable and can be used on demand.
The growing concern over management of municipal solid waste and its direct bearing on the global climate is emphasized in the report “A Global Review of Solid Waste Management,” prepared by the World Bank in 2012.
According to the report, “The global impacts of solid waste are growing fast. Solid waste is a large source of methane, a powerful GHG that is particularly impactful in the short-term. Methane from landfills represents 12 percent of total global methane emissions.” The report indicates that “GHG emissions from municipal solid waste can readily be reduced by generating less waste, improving the efficiency of waste collection, expanding recycling, aerobic composting, anaerobic digestion and incineration waste to energy.”
The development and progression of environmentally friendly WTE technologies that support the above recommendations and address the realization of sustainable solid waste management provide a critical component toward achieving the goals envisioned by COP21.