As recently as 2018, around half of all municipal solid waste generated in the United States went to landfill. That represents an astounding 146.2 million tons of waste in just a single year, for a single country. Changing attitudes to sustainable urban living mean that landfill is increasingly seen as undesirable, and space for landfill is limited in many countries. Coupled with the inescapable fact that fossil fuels are finite, alternatives to burying our waste in the ground are not merely preferable – they’re essential.
Converting that waste into energy is a key element of the fight for a more sustainable way of life and, thanks to technological advances in the field, it’s growing fast. Waste-to-energy conversion is expected to grow by 6.45% per year in the period between 2020 and 2025. But while it seems like an obvious solution to the problem, the waste-to-energy process is not without its own challenges.
Expensive and wasteful?
By far the most common method of producing energy from waste is simply to burn it to produce heat, either for homes or electricity generation. But the incineration plants needed to do this at scale are large and expensive to build and run. Moreover, incineration itself is pollutive and potentially dangerous. Cleaning the gases of the toxic compounds given off by incineration requires sophisticated flue-cleaning technology, for example.
Moreover, the materials burned in waste incineration are often valuable themselves. The process destroys resources which could be extracted and reused or recycled, further contributing to its economic unviability in the long term.
There are examples of combustion being used successfully in waste-to-energy processes. In Varkaus, Finland, the Riikinvoima Ekovoimalaitos Waste-to-Energy plant has been generating 180 GWh of direct heat and 90 GWh of electricity since 2016. It has actually been performing better than expected, using a Fluidised Bed Combustion process that burns waste with great efficiency and reduces pollutant emissions by up to 95%.
While modern combustion technology can produce results like in Finland, there are alternatives to simply burning it. Plastic, increasingly viewed as undesirable in modern society because of its overwhelmingly single-use application, provides a good example of what’s possible.
Plastic has gained notoriety as the worst example of throwaway society. It’s difficult and expensive to recycle, costing as much as $4,000 per ton to do so. Under 5% of it is currently recycled, and much of it ends up floating in our oceans, taking 450 years to biodegrade. But it doesn’t have to be that way, and it’s technology that’s showing us the way forward.
With the right technology, plastic can be converted into fuels that burn cleaner than fossil fuels. It can produce a diesel replacement if treated with hydrocarbon molecules, or even a type of crude oil using pyrolysis. This involves decomposition under high temperatures in an oxygen-free, sealed environment. The benefits are economic, too – the American Chemistry Council estimates that plastic-to-fuel facilities in the United States could generate around 39,000 jobs and $9 billion of economic output.
Critics point out that this does not address the fundamental problem of plastic, which is that it’s too often a single-use material, that the search for ways to use plastic waste should be a search for alternative materials. But its applications are undeniable, and such refuse-derived fuels are already being used in the cement industry, for example. Furthermore, if all the plastic in the US’s municipal solid waste were recycled, it would save nine million tons of waste annually.
For biomass or fossil-fuel-based materials, gasification is an effective way to produce useful substances from waste. The various methods use high-temperature chemical reactions to produce syngas, a fuel-gas mixture of hydrogen, carbon monoxide and occasionally carbon dioxide.
Syngas is combustible and useful fuel because of its many applications. It can be used in internal combustion engines or for electricity generation, where it allows hybrid turbines to operate at lower temperatures, with greater efficiency and over a longer lifespan. It can also be used in the production of diesel or methanol. All of these are valuable resources, and all can be extracted from waste, albeit after considerable processing.
Even landfill can generate fuel
We’ve been putting our waste in the ground ever since industrialisation, but technological advances in methane processing have allowed even landfill to be used to generate energy. Methane, a greenhouse gas 25% more effective than CO2, is a natural product of the decomposition of domestic waste, and landfill is the third-highest human-generated source of this gas.
Landfill gas utilisation traps the methane, treats it and uses it as fuel for combustion or electricity generation. But this process can’t be cost-effectively applied to existing landfills. It must be built into new sites to work properly and be fully economical, when the overall aim should be to eliminate landfill as far as possible.
No single, simple solution
Of course, the ideal solution to our waste problem is to generate much less of it in the first place, and to recycle as much of what we do produce as possible. But the pace of change toward sustainable modern living isn’t yet quick enough for that to come to our aid in the short term.
In the meantime, and probably in the long term, waste-to-energy technology has a key role to play in addressing several problems at once: what to do with our waste, reducing oceanic pollution and providing an alternative to fossil fuels. As in so many challenges facing us today, it’s in new technologies that the most effective solutions lie.
The Collider is a venture-building programme that looks to build such bridges between science, corporations and entrepreneurs. Powered by Mobile World Capital Barcelona, this innovation project aims to drive the transformation of society through tech transfer initiatives, improving the lives of people globally.