What is gasification?

Here’s a quick guide for energy infrastructure owner-operators, developers, investors, EPCs and waste management companies.

Gasification is a misunderstood and largely overlooked technology that offers huge potential benefits when it comes to processing waste, producing sustainable energy, and reducing greenhouse gas emissions in a cost effective way.

Many people mistakenly believe that gasification is ineffective, or that it only works to convert certain feedstocks into energy. At the same time, even many in the waste management and waste to energy industries remain unaware of the wide variety of outputs possible from gasification.

That’s why we decided to put together this quick guide to explain how gasification works and how it might best be applied to today’s most pressing waste management and energy production challenges.

How gasification works - a brief overview

Gasification is a waste-to-energy technology. It takes waste feedstocks and applies heat, oxygen and pressure to convert them into a synthesis gas. Gasification has been around in some form since the late 1700s, when it was used to produce tar. Over the last twenty years, the technology has been refined and developed into what we call “advanced gasification”.

Advanced gasification is the thermochemical transformation of waste feedstocks (carbon-based materials) into a synthesis gas, or ‘syngas’. In contrast to incineration — a more widespread kind of waste to energy technology which burns waste feedstocks in the open presence of oxygen – in gasification, the feedstock materials are converted to a gas (along with byproducts such as ash and biochar) under conditions of high temperature and a highly controlled supply of partial oxygen and/or steam.

The initial gas is then purified to make a ‘pure’ syngas that can then be turned into a useful energy source at a high level of conversion efficiency. These kinds of energy include:

Electricity – with a gas engine or steam cycle.
Heat or Steam – for use in commercial / industrial processes.
Liquid biofuels – using a Fischer-Tropsch gas-to-liquids process.
Bio-Synthetic Natural Gas (Bio-SNG) – can be used in road, rail, air and marine transport vehicles as a substitute for diesel or petrol. Bio-SNG has a much smaller carbon footprint when compared to petroleum products.
Synthetic Natural Gas (SNG) – via a methanation process which can then be injected directly into the gas grid.
Hydrogen – via a process that separates and purifies the hydrogen content of the syngas.

What materials can be gasified?

Gasification works on a huge variety of organic, biodegradable materials. Right now, as the CIWM points out, the technology is most commonly used to convert biomass feedstocks such as wood chips. However, it can actually work on the carbonaceous material in a host of wastes – including what’s known as municipal solid waste.

According the CIWM again, this includes:

Paper
Card
Green waste
“Putrescible waste”
Wood
Plastics — “as they have a high carbonaceous content”

Waste materials such as metals and glass cannot be gasified. However, most of the contents of municipal solid waste contain “carbonaceous” material, and therefore can be.

The universities of Lorraine, France, and Extremadura, Spain, have test facilities based on EQTEC’s advanced gasification technology. As a result of R&D carried out at these locations, we have test results that prove our technology can generate energy from nearly 60 different kinds of feedstocks, including:

Olive stones
Nut shells
Straw
Grape bagasse
Wood chips
Sawdust
Pine cones
Forestry clippings
Lignite
Sludge
Rubber
Demolition rubble
Plastics
Municipal solid waste (MSW) – after recycling also known as refuse-derived fuel (RDF)

Some of these feedstocks require preparation before being gasified, e.g. drying, pelletization. Our technology is very versatile with regards to different feedstocks, but of course we like it when a gasification plant specializes in treating one or two kinds of feedstock, as it will be even more efficient.

The majority of plants constructed by EQTEC are designed and built with specific feedstocks in mind. Our 6MWe capacity plant in Movialsa, Spain, was designed specifically to process local grape bagasse, some time later it switched to olive pits, and since many years the feedstock is now local olive pomace waste, which is converted into heat and electrical energy. Similarly, our plant currently being built at North Fork, California, is designed specifically to process local forestry waste. In plants under design for Greece, we will be using the agricultural waste of three different crop harvests during the year; wheat, corn and cotton.

The gasification process

Once a feedstock is ready for gasification, it is added into a gasifier. There are different types of gasifier, including:

Counter-current fixed bed (“up draft”) gasifier
Co-current fixed bed (“down draft”) gasifier
Entrained flow gasifier
Plasma gasifier
Fluidized bed reactor

EQTEC’s technology is based on the fluidized bed reactor, in which the feedstock is fluidized in oxygen and steam. In any case, the gasifier is where the organic material is converted by partial oxidation into synthesis gas, which comprises carbon monoxide, hydrogen and methane.

The EQTEC advanced gasification process converts waste feedstocks directly and completely into a gas, in a single stage, through a series of thermochemical reactions (called volatilization) in a proprietary, patented bubbling fluidised bed reactor, under conditions of high temperature and a highly controlled supply of oxygen or steam.

Due to considerable advancements in EQTEC’s technology over the years, the syngas produced is already of high quality on exiting the gasification chamber. The syngas is then cleaned and purified through a further series of proprietary technology stages, ultimately producing what is believed to be the highest purity waste-derived syngas. The high purity of the syngas allows gas engines to operate at their maximum output to deliver high levels of electrical efficiency.

Testimonials from leading gas engine company Jenbacher state that “the electrical power could be raised to maximum expected power for this type of gas already during the project commissioning phase, basically due to the high quality and stability of the produced syngas”.

Applications for advanced gasification

As already mentioned above, advanced gasification can produce a host of valuable outputs, including electricity, heat, liquid biofuels, synthetic natural gas, bio-synthetic natural gas, biochar, and hydrogen.

This means that heat and electricity can be used to power local plants, as well as being sold to the local energy grid. Liquid biofuels and green hydrogen in particular are valuable as renewable alternatives to fossil-fuel energy.

Because EQTEC advanced gasification technology can be installed on a modular basis, this makes it ideal for a plant of any scale from 1MWe up to 25MWe. The modular installation means plants can be constructed near to the source of the waste feedstocks being processed, thereby cutting the carbon footprint of a plant. Modular installation also means that plants can be scaled up in line with demand as circumstances allow.

Comparisons with incineration

Incineration produces greenhouse gases, including CO2. The ash incineration produces includes fly ash, which contains toxins such as sulphur dioxide, hydrogen fluoride, nitrogen oxide, silicon dioxide and more. Fly ash may also contain mercury, arsenic, ammonia, cadmium, cobalt, lead and chromium – all poisonous.

As a result, incinerator plants need extensive flue gas treatment for them to meet environmental compliance regulations.

According to a research note from Arden Equity Research:

“A considerable amount of an incineration plant’s infrastructure (and capex) is devoted to the cleaning of exhaust gases. This can also account for significant cost of an incinerator’s operations and can require further replacement of consumables.”

Arden Equity Research Tweet

Advanced gasification, by contrast, creates 25-30% lower greenhouse gas emissions than incineration. It also produces no fly ash or other pollutants.

Incineration also faces an uncertain future. In December 2019, the European Commission agreed to “exclude incineration from its list of activities that advance climate change mitigation… stating that minimising incineration and avoiding disposal of waste will contribute to the circular economy”. This decision follows a prior agreement to phase out subsidies to incinerator plants in the EU.

Advanced gasification faces no such regulatory uncertainty. Indeed, as a source of green hydrogen, it may even receive a boost in investment via the European Union’s Green Hydrogen Strategy, which seeks to promote increased use of green hydrogen in all sectors of the EU economy — with a particularly strong focus on transport and on energy production.

For more information on the comparisons between advanced gasification and waste incineration, read our article Energy from waste: the pros and cons of advanced gasification versus incineration.

The benefits of advanced gasification

In short then, advanced gasification is a waste to energy technology which has the potential to usurp incineration as the best-in-class technology for waste-to-energy production at a time when waste volumes and global demand for energy are both forecast to rise significantly. It is a technology that is proven, proprietary and economically viable — as well as much more sustainable than incineration. It also, critically, has enormous potential as a source of renewable energy. It has a great track record and a wide variety of potential applications. Use of advanced gasification helps to promote recycling, along with other aspects of the circular economy.

For waste management companies, local authorities, EPCs, energy infrastructure owner-operators, developers and investors, and other waste-to-energy stakeholders, advanced gasification is likely to loom large in their future as incineration loses favour.

By Dr. Yoel Alemán, CTO, EQTEC plc

Syngas for carbon-efficient waste conversion and new energy infrastructure