October 14, 2006

Geoplasma Answers Trash Vaporization Questions

On September 10th I drafted an article about a plan to use plasma-arc technology to gasify waste in St. Lucie County, Florida titled FLORIDA: County to Vaporize Trash. In addition to writing my concerns about the emissions from the process, I listed five questions that I wanted to have clarified by the developer, Geoplasma of Atlanta, Georgia. I sent the list to the president of Geoplasma, Hilburn Hillestad, who very graciously sent me the following reply:

Response to BioConversion Blog Questions about Trash Vaporization
From Hilburn Hillestad, President of Geoplasma, LLC.

Below you will find our answers to your questions. Thank you for your interest in our proposed facility.

1. Question: How much energy does the plasma-arc use?
The plasma-arc facility uses approximately 40 megawatts of energy per hour. This is approximately one-quarter of the total output of hourly energy received from MSW.

2. Question: What will be the source of the plasma-arc energy?
The facility will receive its energy from its total output. For St. Lucie, it is expected that the 3,000 tons of MSW processed per day will create 160 megawatts of energy per hour. As stated previously, 40 megawatts will be used to power the facility and the remaining 120 megawatts will be sold to an Electric Utility.

3. Question: What does the energy source emit?
See question 5.

4. Question: Is the high heat of the plasma-arc being captured and utilized?
Because of the nature of a closed-loop system the heat will be captured and utilized both in the plasma gasification process and later in the production of steam.

5. Question: How are they going to combust the syngas to keep the emissions low?
There is no combustion during the gasification process. The Plasma-arc gasification process is a chemical reduction process that converts MSW from its original state to a glass-like aggregate solid at the bottom, and a synthetic fuel gas, also known as syngas, at the top.

Once gasification is over, the syngas is cleaned in a multi-step process, bringing it to levels near natural gas cleanliness. It is then compressed before being used as fuel for a gas turbine.

The gas turbine for this process is a modified natural gas turbine that mixes the cleaned syngas with air from the atmosphere, combusts the mixture and sends the hot gases through a turbine. The turbine spins an electric generator to produce electricity. The discharged hot gases are then passed through a heat recovery steam generator to produce more steam and to cool the hot gases. The cooler exhaust gases are then discharged into the atmosphere via a stack.

Emissions from this process are very similar to natural gas combined cycle plants which are considered to be ‘clean’ and are located and permitted all over the U.S., and for that matter the whole world.

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Kody said...

Two further questions:
1. The president states, Once gasification is over, the syngas is cleaned in a multi-step process, bringing it to levels near natural gas cleanliness.. What exactly is cleaned from the syngas (heavy metals? dioxins?), and what is done with this "unclean" portion?

2. What is done with the glass-like aggregate solid? It sounds like this could either be a useful byproduct or a really nasty byproduct.

C. Scott Miller said...

Gasification systems usually incorporate "scrubbers" (see the wiki definition) to remove unwanted elements from the syngas.

What the actual gas residues are segregated depends on the feedstock being gasified - whatever isn't carbon, hydrogen, or oxygen is typically what is being scrubbed. They can be very effective leaving toxic emissions at a mere fraction of current regulations for toxins, dioxins, or nitrous oxides - far healthier than what is being emitted from the status quo processing (or landfilling) of these feedstocks. If the scrubbers output was concentrated enough - like gasified sulfurous coal yielding sulfur - you could resell it to chemical companies.

Also look under "waste management" in Wikipedia to learn more about plasma gasification. Usually the solid byproducts are crushed and used in inocuous ways - like blended fillers for paving materials. You wouldn't use it to gasify radioactive wastes.

Anonymous said...

What is the installed cost for this system?

C. Scott Miller said...

You'll have to ask the manufacturer - I don't know.

I think the real question for all these technologies is - what is the system worth? I can easily imagine enzymatic systems being cheaper to install as front ends of existing corn fermentation plants. But syngas gasifiers would more likely be found near urban centers. Both solve problems - their value will determine whether their prices are worth it.

Anonymous said...

I compare the capital cost of systems by figuring the $ per Million BTU of end use energy produced over 20 years, just as a rough guideline. If I can get this info I'll pass it along to you.

The ROI is a function of the value of the end use energy produced and sold.

C. Scott Miller said...

Thanks Barry,

For surfers of this blog I highly recommend reading Barry's book "Energy Power Shift." Barry has a great overview of the many decentralized power generation systems that can contribute to sustaining a secure and clean supply of energy.

Anonymous said...

The last time I checked, they wern't making anymore land so it seems like a good idea not to contaminate what we have left. But like everything else that is good in the world, it's just a matter of time before some terrorist dumps something into the process that queers the whole operation.

Anonymous said...

USA Today reported plant cost at $425 million in 2006

Anonymous said...

I recently came accross your blog and have been reading along. I thought I would leave my first comment. I dont know what to say except that I have enjoyed reading. Nice blog. I will keep visiting this blog very often.



Unknown said...

landfills create terrible environmental problems; toxins leaching into the water table, methane gas emissions, piles of ugly, windblown trash. If we can convert the mess into energy, then we are solving the trash problem along with reducing the need to extract more fossil fuels, which are definitely not clean. Every piece of trash represents embodied energy which was used to extract the raw materials and convert them into a product with a short shelf life. Tearing the trash down to its constituent molecules and producing gas/heat/electricity looks like recycling to me. It may not be as ideal as traditional recycling/reducing/producing less trash in the first place, but I would rather mine a landfill for energy than drill in the Arctic wildlife refuge, scrape the tops off of mountains digging for coal, or revive the nuclear power industry. Municipal waste is only the tip of the iceberg. Add in the refuse from industrial meat processing, human and animal sewage, agricultural residues, sludge from pulp mills and lumber factories, and so on, and we have the potential to make a serious dent in the need for fossil fuels. No doubt there are drawbacks, some negative aspect to the process. there always is. We need to weigh those drawbacks against the problems we already have, of waste disposal and environmental destruction. trash production and demand for energy are both increasing every year. If we can make a closed loop out of eliminating waste and producing energy, then I say monitor the stacks for toxic emissions, control it like any other regulated industry, and go for it. my humble opinion. deanna.