A zero-waste system offers an excellent opportunity to reduce GHG emissions, and many countries have aimed to become Net Zero by 2030.
A zero-waste system means reducing waste and changing how we produce, consume, and dispose of our stuff. It also promotes the use of recycling, reuse, and composting. As half of our emissions come from the extraction and processing of materials, including food, adopting this system will allow us to reduce our emissions and waste, which is also a significant source of GHG emissions and pollution.
But with the rapidly increasing worldwide waste – most of it ends up in landfills, which is a significant source of methane emissions – a more powerful planet-warming gas than CO2, are there other solutions to reduce the residual waste after implementing the zero-waste system?
Waste-to-energy to reach zero waste
Waste-to-energy is put forward as one of the solutions to reduce waste while generating energy to address growing electricity demands. Waste-to-energy solutions use incineration, pyrolysis, gasification, or a combination of these processes. According to Project Drawdown’s article, Waste to Energy, converting waste to energy could avoid 6.27–5.24 gigatons of greenhouse gas emissions by 2050 due to reduced methane emissions from landfills and reduced demand for fossil fuels. The approach could be a transition solution that can gradually decline as zero-waste systems (reuse, recycling, and composting) gain widespread adoption. However, with the apparent advantages of waste-to-energy in reducing waste and producing energy, these plants can create health and environmental risks.
The article notes that the conversion of waste to energy has been widely adopted in Europe and Japan and is also growing in China. Countries in the Organisation for Economic Co-operation and Development (OECD) are most likely to implement the system in the future.
Waste-to-energy technology that uses conventional incinerators to reduce waste and produce heat or electricity in the process, like those used in some EU nations, has obvious advantages – lowering waste that should otherwise be taken to landfills while creating electricity and recovery of some materials like metal after incineration, it comes with some challenges. First, it is not as clean as advertised.
The problem with incinerators, according to Greenpeace, is that they produce toxic ash waste (up to 20% of the weight of the waste and 10% of its volume) and toxic emissions that escape from the chimney filters, such as dioxin, an invisible and cancer-causing pollutant.
But what if there is a way to eliminate or reduce the toxic ash to 3% with the residual waste treated and completely recycled?
Japan’s waste gasification and direct melting technology
This is the technology that has been developed in Japan. A waste-to-energy technology using gasification technology (direct melting system). Waste gasification almost eliminates residual ash, produces high-quality slag and metal that can be completely recycled and sold, and produces very few pollutants.
A paper by Steinmüller Babcock Environment GmbH (SBENG), a subsidiary of Nippon Steel & Sumikin Engineering Co., Waste Gasification Technology (Direct melting System) explains how the system can reduce pollutants, “The use of limestone in the gasification process minimises the emission of hydrogen chloride and sulphur dioxide, and homogeneous syngas combustion enables a reduction in dioxins and furans in a secondary combustion chamber. An optimised flue gas treatment minimises the environmental impact. Therefore, considerably fewer pollutants are emitted at the stack than are allowed by strict European regulations.”
This system also boasts low-emissions, high-efficiency, high-energy generation, and lower air pollution than conventional incinerators.
Nobuhiro Tanigaki, Senior Manager at Nippon Steel Engineering, the market leader in Japan, which has built more than 50 gasification plants, explains the benefits of using a direct melting system (DMS). “The final landfill amount from grate in Japan is approximately 15%, while the final landfill from our Direct Melting System is only 3%. It contains only the Air Pollution Control residue, whereas the landfill from conventional grate technology contains bottom ash and APC residue. The gap is the benefit as the landfill costs of bottom ash and APC residue are almost the same. In addition, DMS co-gasification of other waste that is difficult to treat, such as rejects from recycling centres, incombustible or reclamation waste, would help to minimise the final landfill as well” (Waste to energy, 2023).
When did the waste-to-energy start in Japan?
During the oil crisis, Japan developed energy recovery technology from waste in the 1970s. Interest increased in converting household waste into energy and recycling resources. Nippon Steel & Sumikin Engineering Co., Ltd. first introduced the Direct Melting System (DMS), a gasification and melting technology, in 1979 in the city of Kamaishi. This is when the country is exp during the oil crisis. The technique has been used commercially for 40 years at more than 50 sites in Japan.
Capacities of DMS range from 10,000 to 230,000 tonnes of waste per year. DMS facilitates a zero-waste policy thanks to the almost 100% reusability of the end products.
Additionally, due to the high temperatures of the DNS, the system can treat all types of waste, from household waste to bottom ash, special waste to clinical waste and the gasification of sewage sludge. The energy produced from the plants is fed into the public grid.
Can the technology benefit other countries that have similar issues as Japan?
According to the Waste Management World article, Waste to Energy: Lessons from Japan, the main objections to waste gasification are its costs – it is too expensive, maintenance intensive, and inefficient in comparison with the conventional incineration plants, which is why only gasification application in high-income countries only accounts for 2% while in low-income countries it is non-existent.
While incinerators have been widely used in Japan, waste gasification and direct melt came about when the government required to reduce or eliminate the ash residues, leading them to develop a two-stage waste treatment process.
The United Nations Industrial Development Organization article, Eco-Friendly Waste Gasification & Incineration System for Energy Generation, explains how the two-compartment combustion system works. “In this system, gasification and combustion occur in two different compartments. The separated compartments contribute to the efficient combustion of waste (the combustion efficiency is almost 100%, and the loss on ignition is 3% or less.) into usable energy such as electricity, steam, hot water, and hot wind. Stable combustion can be achieved in tightly sealed compartments, reducing fossil fuel use”.
“The resulting inorganic ash can be safely recycled. They are used as a material to compose cement and pavement.”
The rapidly growing amount of waste worldwide and the need to dispose of it sustainably and in a way that does not pollute the environment and add to global emissions could benefit from Japan’s waste-to-energy technology. With continuous technological improvements, it can soon become a viable and feasible waste disposal and energy source for other countries.
DMS has been successfully implemented in Japan due to its highly restrictive landfill policy stemming from waste management system laws that allowed the country to overcome the technological challenges of building and applying gasification.
For example, municipalities must create a long-term waste management plan for at least the next 10 years and treat and recycle their waste. Japan’s geography is also another contributing factor. It limits their use for landfills, which makes DMS a viable alternative.
Waste Gasification Technology (Direct Melting System). (n.d.) Steinmüller Babcock Environment. Retrieved from https://www.hzi-steinmueller.com/wp-content/uploads/downloads/broschure-waste-gasification-en.pdf
Szabo, M. (2021, November 26). Burning rubbish creates toxic waste and fuels climate change. Greenpeace. Retrieved from https://www.greenpeace.org/aotearoa/story/burning-rubbish-creates-toxic-waste-and-fuels-climate-change/
Waste to energy: Lessons from Japan. (2023, May 10). Waste-Management World. Retrieved from https://waste-management-world.com/waste-to-energy/waste-to-energy-lessons-from-japan/
Eco-Friendly Waste Gasification & Incineration System for Energy Generation. (n.d.). United Nations Industrial Development Organization. Retrieved from http://www.unido.or.jp/en/technology_db/1647/
How much methane is generated by the global landfilling of urban wastes? (2023, April 3). Waste-Management World. Retrieved from https://waste-management-world.com/resource-use/how-much-methane-is-generated-by-the-global-landfilling-of-urban-wastes/