Aries Clean Energy
February 13, 2019
Gasification is flexible not only to what feedstocks it can use but to what end is needed from its conversion process. Clean, renewable electrical generation behind the meter and creation of Class A biosolids are possible through gasification. And the leftover biochar is gaining popularity and being further examined for new uses and possible new revenue streams.
Multiple feedstock streams – creating Class A biosolids – clean, renewable electrical generation – Gasification unlocks the flexibility of clean energy – Aries Clean Energy can help.
Gasification has been around for a long time, and it is widely used in Europe. It is just now growing in popularity in the United States. In recent years, the research has paid off with new technologies that make the process more efficient with less maintenance required.
When organic materials are heated in an oxygen-starved, pressurized environment, the materials cannot ignite. The heat forces the complex carbon molecules to break apart forming a mixture of gases, called producer gas or synthetic gas. This gas can be combusted to produce electricity or steamed off without harming the atmosphere. All the organic materials are not converted to gas – part of them reform into a material called biochar, a carbon-rich soil amendment (more on that later). This environmentally friendly process is known as gasification.
To cite a recent EPA report entitled Technology Assessment Report – Aqueous Sludge Gasification Technologies:
Gasification offers a potentially viable option compared to conventional methods for sludge disposal. Gasification is capable of providing a clean and manageable process with the possibility of net energy gains. The variability and lack of information on commercial scale systems however, makes it difficult to ensure a complete analysis and concrete conclusions on sludge gasification’s viability. ¹
So, what can be done with the syngas produced in the process? See three examples below.
Three options of gasification process flow
Multi-feedstock Electrical Production – In this example, multiple feedstocks are acceptable for biomass gasification. This can result in more organic material being diverted from landfills and that will lower local carbon footprints. A perfect, clean-energy storm exists for locations near wastewater treatment plants as the plant’s sludge now becomes a feedstock and not an addition to the local landfill. And the wood waste from discarded pallets of local businesses and rights of ways’ street and park trimmings can be utilized, too. In addition, water from the plant can also be cycled through the gasification plant to be used for cooling instead of industrial fans or to power Organic Rankine Cylinder generators to produce power behind the meter. This method also eliminates costs associated with transportation of sludge disposal.
The multiple feedstocks are sized and dried for best efficiency, then mixed together before entering the gasification chamber. The producer gas is sent to a thermal oxidizer where it is ignited and the energy from that is used for power generation or used to fuel a steam turbine that can power boilers, sludge dryers, or kilns. Electrical generation can be used to offset current electrical utility costs or to supplement power needs. All gasification processes will have a leftover product – called biochar – that has value and can be repurposed further as a soil enhancement, carbon black production, etc.²
Examples of tested and proven feedstock include:
- Industrial or municipal sludge
- Food processing wastes
- Chips from wood waste or forest residuals
- Purpose-grown biomass crops
- Crumbed tires
- Ag waste such as corn or cotton stalks
- Processed and pelletized municipal solid waste
Wood Waste to Power – A wood waste feedstock plant is ideal for industries with solid wood waste streams. Examples would be hardwood floor or cabinet manufacturing. Also companies with increasing loads of broken wood pallets that want to eliminate landfill trips and their associated costs. With a wood feedstock only, there is no mixing of materials. The chipped wood goes directly into the gasification reactor. From there, the syn gas goes into the thermal oxidizer where it is combusted and the energy used to run a generator or kiln, etc.
Creating Class A Biosolids – The EPA defines Class A biosolids as biosolids that contain no detectible levels of pathogens. Class A biosolids that meet strict vector attraction reduction requirements and low levels metals contents, only have to apply for permits to ensure that these very tough standards have been met. It further states that anyone who wants to use biosolids for land application must comply with all relevant federal and state regulations. In some cases a permit may be required. ³
As we have said above about the gasification process, wood is converted into a producer gas that can, when combusted, use that energy to fuel a sludge dryer. The sludge dryer will convert the sludge into a Class A material. Also, the condensed steam generated during this process can also be sent back to the wastewater treatment company for other uses.
Benefits of biochar via gasification:
- Biochar can be used as a soil amendment (farmers, golf courses, city and state parks)
- Industries readily purchase carbon black that can be made from biochar. The EPA defines carbon black as a black, powder or granular substance made by burning hydrocarbons in a limited supply of air. Uses for carbon black include automotive belts and hoses, industrial rubber products, paint, inks, plastics, ceramics and tire production.³
- Opportunities for partnerships with local industry, municipal leaders
- New revenue stream for gasification plant owners
- Markets alleviate owners from transportation disposal costs
- The gasification process takes harmful particulates out of solid waste streams
- For more information and to catch up on some recent biochar agricultural research by the University of Tennessee, please see this recent article from Bioenergy Insight https://ariescleanenergy.com/article-biochar-opportunities-knock-agricultural-research-may-open-tennessee-biochar-market/ (photo shows seedling started in biochar only, courtesy of Kim Lehiö)
- Or check out The Biochar Journal at https://www.biochar-journal.org/en
Gasification is flexible not only to what feedstocks it can use but to what end is needed from its conversion process. Clean, renewable electrical generation behind the meter and creation of Class A biosolids are possible through gasification. And the leftover biochar is gaining popularity and being further examined for new uses and possible new revenue streams. Questions? Find more on our website at www.ariescleanenergy.com. Or you may contact Aries Clean Energy at email@example.com or 615.471.9299 for more information.