New advanced technologies can produce energy from municipal solid waste. Homes and households produce 60 percent of the waste, and people will always create garbage. Thus, the conversion of municipal waste into an energy source can become one of the largest energy sources of the future.
For every ton of household waste produced, commercial, industrial and construction businesses produce another six tonnes. Manufacturers can minimize and improve their waste management in order no longer to be able to discard their waste.
Along with the “Zero Waste” approach, other alternative methods for managing the household and commercial waste that reduce the amount of harmful waste, including industrial toxic by-products, are the so-called “Waste-to-Energy” technologies that generate energy from waste.
The municipal waste separation and recycling methods greatly reduce the amount of solid waste left over, which means much less space in landfills. However, a vast portion of mixed waste or residual waste is difficult to separate and recycle. Waste feedstock left after sorting is standardized into solid recovered fuel (SRF) or refuse-derived fuel (RDF).
There are various applications of Waste to Energy (WTE), which are based on gasification, pyrolysis, and incineration. The energy produced by gasification is considered renewable in some U.S. states.
What is Gasification?
Gasification is a process of breaking down the organic matter into a gas by applying extreme temperatures in an environment with a limited amount of oxygen.
The gasification system breaks down the organic waste into a gaseous form bypassing the 4 processes such as drying, pyrolysis, combustion, and reduction.
Pyrolysis is the application of heat to the organic matter in the absence of any oxygen. The solid waste breaks down into charcoal and various tar gasses and liquids. It is essentially the process of charring.
A heat source is required for the pyrolysis process, but no heat source is needed for gasification because this process is self-sustaining thermally.
When both pyrolysis and gasification processes occur at the same time, the gasification combustion reactions can provide the heat source needed for the pyrolysis process to perform the reactions.
Gasification and pyrolysis produce synthetic gas or Syngas as a major end product of the process. Syngas is similar to natural gas that contains a mixture of hydrogen, carbon dioxide, methane, carbon monoxide, and other hydrocarbons and inert ingredients.
The produced Syngas is cleaned from large tars and particulate goes through several steps of the filtration system. The cleanliness of the gas is important for the end-use. It can be used to power an internal combustion engine, feed a boiler or a burner and could be used to create steam.
This gas can be used to power an internal combustion engine in order to create electricity. This makes both pyrolysis and gasification methods profitable, because of the various end products from Syngas including heat and power generation.
Gasification vs Incineration
Although the two processes have some common features it’s important to understand the difference between them.
Incineration is the process of combusting the organic matter within waste through ‘thermal treatment’. The main by-products of incineration are inert bottom ash and the flue gas. The toxic dioxins and furans are formed, especially when PVC-containing plastics and other materials are burned. Pollution Control Systems (PCS) destroy these gases by passing through a secondary burner at high temperatures.
On the contrary, gasification is claimed to be a carbon-neutral process. It fits into the carbon-cycle by using responsibly sourced biomass as fuel.
As a result, incineration produces just heat and electricity, while Syngas produced by gasification can be turned into valuable commercial products including transportation fuels, chemicals, and fertilizers.
Emissions from gasification are below EPA emission standards. This explains the growing trend in the development of gasification based waste-to-energy, which is considered renewable energy.
Waste-to-Energy Plants in Europe
Waste-to-Energy (W2E) is widely used by the EU countries to burn waste that could not be recycled. This waste is used to generate energy in the form of steam, electricity or hot water.
Modern Waste-to-Energy facilities are equipped with filters. Between 1990 and 2000 dioxin emissions of Waste-to-Energy plants in Germany dropped from 400 g to less than 0.5 g per year while the amount of thermally treated waste had more than doubled in the same period.
Waste-to-Energy supports high-quality recycling. Countries with very high recycling rates also have high rates of Waste-to-Energy and thus have reduced landfills to almost zero. These are Austria, Belgium, Germany, and the Netherlands. New Waste-to-Energy initiatives have been also introduced in Italy, Romania, Bulgaria, and the Baltic countries.
Has Sweden established the best recycling practice?
Sweden burns 2 million tons of waste every year, while only 1 percent of all country’s household garbage goes into landfills. Half of the waste is recycled while another half is burned. The country generates 40 percent of heat energy by burning garbage in low-carbon incinerators or Waste-to-Energy plants.
The Waste-to-Energy system also improved Sweden’s recycling rate by 50 percent, which is twice as much as the US rate of 24 percent.
Sweden banned landfills in the 2000s and considers waste incineration as a form of recycling. According to some reports, up to 86 percent of plastics in the country is burned. It is known that burning plastic is very harmful to human health and the environment. However, the Confederation of European Waste-to-Energy Plants (CEWEP) claims that there are no harmful effects.
The country runs out of garbage and imports it from other countries. Currently, Sweden imports about 700,000 tons of garbage from other European countries including the UK and Norway.
Debates Over Waste-to-Energy
Waste-to-Energy plants provide energy and reduce a significant amount of non-reusable, non-recyclable waste by 90 percent. But is this energy renewable, as it is claimed?
There is disagreement with environmental justice communities and non-governmental organizations. The Global Alliance for Incinerator Alternatives (GAIA) report (May 2019) shows that municipal waste incinerators are economically inefficient as the most costly and unsustainable, and also raise growing concerns about health effects.
Energy Justice Network considers incineration as an extremely dirty way of getting rid of waste. Waste incineration produces highly toxic emissions of dioxins, furans, mercury, lead, and other toxic substances. A 2006 EPA study found that dioxins, highly toxic substances produced by incinerators can cause cancer.
EPA emission standards for incineration plants are currently being criticized in court by Earthjustice, the environmental legal organization representing Sierra Club to address pollution issues under the Clean Air Act.
Zero Waste Europe is convinced that “Waste-to-Energy is not sustainable because it harms the Circular Economy.” Burning garbage and releasing carbon dioxide minimizes all the benefits of landfill reduction.
Waste-to-energy plants dispose of waste including single-use plastics and other recyclable materials, through the processes of incineration, pyrolysis, gasification, and a plasma arc system which are considered as “waste-of-energy”.
Recently, waste-to-energy incineration was excluded from the new E.U. Sustainable Finance Taxonomy Report (June 2019). Transition to a Circular Economy, waste prevention and recycling are major environmental objectives that can contribute to climate change mitigation as well as to the E.U. climate goals in accordance with the Paris Agreement.
With the implementation of green initiatives and more sustainable waste management, the expansion of landfills has rapidly slowed. Environmentally friendly technologies and waste separation methods must meet strict environmental pollution standards.
Building a Circular Economy that includes the prevention, reduction, reuse, recycling and repair of waste will largely depend on changes in our behavior and the adoption of a sustainable lifestyle. The next generation can deal with these problems better than we do.
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