The Difference Between Gasification and Incineration

I recently received an e-mail from a concerned citizen of Ontario. Jane Wilson was very upset with me because she'd heard my firm is planning to build a waste to energy plant in Sarnia, Ontario. She went on to say that it is impossible to run an incinerator without any emissions. Funnily enough I pretty much agree with her.

I tried to explain the difference between incineration and gasification, but she was not having any of it. She told me it was just semantics. Apparently she is a chemist and this gave her superior knowledge about such subjects.

Seeing that I was unable to get her to listen, let me set the record straight about these two issues.

Admittedly there are similarities, but that does not make them the same or the consequences of using them the same.

Incineration is simply burning. Burning requires oxygen either in the air or as a pure feed. When a substance is burnt, it is oxidized. If we burn hydrocarbons like those found in waste we typically get lots of CO2 and some water H2O. Waste is seldom pure and a lot of toxic substances are formed. These toxic substances are released to the atmosphere in smoke if it is not scrubbbed.

I was going to give you my own definition of gasification, but thought an independent 3rd party view might remove any bias that I have. Here's what Wikipedia says:

"Gasification is a process that converts carbonaceous materials, such as coal, petroleum, biofuel, or biomass, into carbon monoxide and hydrogen by reacting the raw material, such as house waste, or compost at high temperatures with a controlled amount of oxygen and/or steam. The resulting gas mixture is called synthesis gas or syngas and is itself a fuel. Gasification is a method for extracting energy from many different types of organic materials.

The advantage of gasification is that using the syngas is potentially more efficient than direct combustion of the original fuel because it can be combusted at higher temperatures or even in fuel cells, so that the thermodynamic upper limit to the efficiency defined by Carnot's rule is higher or not applicable. Syngas may be burned directly in internal combustion engines, used to produce methanol and hydrogen, or converted via the Fischer-Tropsch process into synthetic fuel. Gasification can also begin with materials that are not otherwise useful fuels, such as biomass or organic waste. In addition, the high-temperature combustion refines out corrosive ash elements such as chloride and potassium, allowing clean gas production from otherwise problematic fuels.

Gasification of fossil fuels is currently widely used on industrial scales to generate electricity. However, almost any type of organic material can be used as the raw material for gasification, such as wood, biomass, or even plastic waste."

Plasma gasification runs at about 5,500 degrees Celsius and immediately breaks everything down to its basic molecular structure. The only residue is an inert vitrified slag which can be used to make aggregate for construction.

You can learn more about gasification with this YouTube video.

As you can see the two processes are quite different and gasification offers a number of distinct advantages over incineration.

It is true that gasification does release some CO2, but that is generally less than what is produced by incineration.

Incineration can be used to create heat and steam for the generation of electricity, but the syngas produced by gasification can be used to make a number of value added commodities including liquid fuels like green diesel and ethanol.

What is recycling at the molecular level?

We owe the quality of our lives to our ability take resources and turn them into products we need.

The products we need are then used or consumed and what we don't want is thrown out.

What we throw out goes to be recycled or land filled. Less than 50 % of what we dispose of is recycled, the rest is dumped in landfill for future generations to worry about.

Most of us acknowledge that landfills are a necessary evil, what we don't question much are the alternatives to landfill.

The way we handle waste today assumes waste is a liability.
What if we were to assume that waste is a valuable distributed energy resource? It in fact contains, on a ton for ton basis, about 50% of the energy of coal.

How would we handle it then?

It would become clear that disposal is the lowest level of use for a resource. Incineration is little better. Granted, we can use the energy we generate to fire kilns or create steam for generators, but in reality this is very low level recovery.

We can improve our ability to recycle and I think this is happening all the time, but much of what goes to land fill is beyond recycling as it is currently done. It is a mixture of a wide range of materials, some of it rotting and odorous, much of it is moist and each component contaminates the other components. So what do we do with this stuff?

We tend to think of recycling at a product level. Paper is recyclable, metal is recyclable, glass is recyclable and so are plastics. But what if we look at this material at the molecular level?

Much of what goes to landfill has high levels of carbon. Items such as organics, paper, plastics fibres, carpeting, wood rubber and even asphalt shingles all contain carbon along with hydrogen and oxygen. These elements are bound together in a variety of complex compounds often containing other elements as well.

But instead of thinking about this material at a product level, what if we viewed it at the molecular level? We'd see that it contains valuable energy and compounds which can be transformed into other valuable resources.

We can take this material, vaporize it so it breaks down to its basic molecules. Once we've done this, we can produce what is known as syngas. Syngas is a combination of carbon monoxide and hydrogen and these two components can be used to make a wide variety of valuable fuels and chemical feed stocks. These can either be used as fuels or used as resources to make other useful products.

This is recycling at the molecular level.

It assumes waste has value and in fact enables us to put a value on municipal solid waste. If one takes into account what can be made and sold from MSW, a rough back of the envelope calculation shows that each ton of garbage may be worth around $300 a ton. This technology exists, is available and will become the norm sometime in the near future. More can be learned about this process at www.alternativefuelscorp.com

If that's the case, what we dump in landfill in North America each year may be worth upwards of $70 billion.

Do we want to keep burying it in a hole in the ground or do we want to turn it into something useful, thereby cleaning up the environment, reducing methane escape into the atmosphere and eventually getting rid of landfill altogether?