FastOx Gasifier Feedstock Overview
FastOx gasification can accept most wastes. Learn more about the types of acceptable wastes and the flexibility of FastOx gasification.
What is Essential to FastOx Gasification?
Sierra Energy focuses on converting non-recyclable trash into energy. Based on that principal, our FastOx gasifiers have been developed to create energy-dense syngas from the elemental carbon contained within waste materials. In FastOx gasification, monitoring the amount of carbon entering the gasifier is essential as it dictates the amount of oxygen and steam necessary to optimize the energy production of our system. Without a sufficient source of carbon the system will struggle to operate at an optimal level.
All other waste properties, such as moisture content and size, affect the efficiency of the overall system but are controlled using our preprocessing systems. Therefore, these factors should be considered during the system design stage to ensure that the optimal configuration is used to handle each unique feedstock.
Prior to all projects, Sierra Energy performs a feasibility study to address these considerations.
Learn more about the economics of processing your desired waste stream via FastOx gasification by visiting our calculator tool.
Acceptable Waste Types for FastOx Gasification
Often, interested parties ask if a FastOx gasifier can accept a certain type of waste. However, FastOx systems can accept such a broad ranch of feedstocks and waste types that a better question would be: "what is the optimal combination of wastes to produce the most energy?"
While the combinations of waste types needed to optimize energy production may change, almost any type of waste are acceptable. This includes: municipal solid waste (MSW), biomass, auto shredder residue (ASR), railroad ties, medical waste, hazardous waste, tires, construction & demolition waste, industrial waste, and more. The only type of waste not recommend for processing is radioactive waste.
MSW and biomass are ideal feedstocks for FastOx gasification. The EPA defines MSW as waste consisting of everyday items "used and then thrown away, such as product packaging, grass clippings, furniture, clothing, bottles, food scraps, newspapers, appliances, paint, and batteries,” which come from “homes, schools, hospitals, and businesses” (US Environmental Protection Agency, 2013). MSW makes a great feedstock for FastOx gasification due to its abundance and its variable composition which tends to optimize the gasification process. Biomass, another readily available feedstock, is defined as materials whose original source comes from plants and animals. Due to its carbon abundance, biomass offers an energy-rich feedstock option that is fully renewable.
FastOx gasification's feedstock flexibility makes it a perfect back-end system for a materials recycling facility (MRF). Using a FastOx gasifier, non-recyclables from the MRF can be efficiently and economically rendered into renewable energy. This prevents the MRF from taking on the liability of sequestering leftover waste or paying to have it landfilled. Contact us to learn more about our gasification system's ability to supplement existing recycling and other waste handling programs.
While FastOx gasification can readily accept most waste forms, there are some materials that are acceptable though not well suited for the FastOx system. These waste types are classified as reluctant waste.
Sierra Energy defines reluctant wastes as those that would need to be examined more closely before determining their effectiveness in FastOx gasifiers. Reasons for this reluctance can vary but is based in the need for more information regarding the composition and elemental makeup of each material to predict their efficiency in the gasifier. We classify reluctant waste as the following:
- Wet waste
- Waste with low amounts of carbon
- Oil-based drilling mud
- Raw sewage
- Grey water
- Cooking oil
It is not thermodynamically optimal or economically efficient to use these wastes as the primary feedstock components for a FastOx gasifier. The technology will still function if they are used, but the system runs more efficiently if used in combination with other waste streams. If you have access to these types of waste and are interested in exploring the implications of using them in FastOx gasification, please contact us to discuss the possibilities for your gasification project.
Unacceptable Waste for FastOx Gasification
The only feedstock that cannot be accepted by FastOx gasification systems is radioactive waste.
FastOx gasification can accept all other types of waste.
The size of the top of the gasifier vessel constrains the acceptable size of the feedstock size. Thus, we must size feedstock appropriately to ensure efficient gasification.
The size of the material entering the FastOx gasifier will depend primarily on the system size. For our small-scale, 10-25 metric tons per day (MTPD) systems, the bulk waste material will be shredded to approximately 1-3 inches with smaller dust and particles also being allowed into the gasifier. For larger scale systems (100 MTPD+), the material will be sized to roughly 6 inches or less.
In addition to being necessary for fitting waste into the gasifier, shredding waste helps to increase the efficiency of the system by increasing the surface area and number of reaction sites of the feedstock. This increases the reaction speed. The smaller materials can also absorb heat faster. Finally, shredding the feedstock blends the materials before entry into the gasifier to ensure an even distribution of reactants in the vessel.
Sierra Energy is currently exploring designs for a system that could accept whole, unopened trash bags and containers of medical and hazardous wastes.
Are there feedstock constituents that will cause issues with the technology?
The primary consideration for the FastOx system is optimizing energy production. Therefore, one of the goals of preprocessing is identifying and eliminating components of the waste stream that make the process less efficient. For example, feedstock with a high moisture content will consume large amounts of energy as the water evaporates. It is more desirable for this energy to be consumed during syngas production. To avoid this loss in efficiency, our system is designed to dry waste to approximately 20% moisture content before sending it into the gasifier. Even though the system runs optimally with dryer feedstocks, high moisture content only causes a minor loss in efficiency in a FastOx system whereas high moisture content creates serious technical issues in other systems.
Feedstocks with high thermal stability, such as certain ceramics and some titanium alloys, may be included as a component of a feedstock but will pass through the system unchanged and will not contribute to energy generation. To avoid the minor loss in system efficiency from processing waste that will not break down, these materials may be sorted out prior to entering the gasifier. Though sorting is recommended, it is not required as these materials will not damage the system.
Can You Gasify Coal with FastOx Gasifiers?
Yes. Coal gasification is highly efficient as coal is energy-dense and rich in carbon. However, there are many environmental consequences that discourage Sierra Energy from pursuing systems focused on coal gasification. The primary drawback is pollution via the release of new carbon into the atmosphere. This not only causes disconcerting levels of damage in local areas but also contributes to global greenhouse gas accumulation and ultimately contributes to climate change.
FastOx gasification can accept coal fines. Given its carbon-rich nature, coal makes an excellent feedstock for FastOx gasification, even when it comes in small quantities such as coal fines. However, it is not recommended that an entire system run exclusively on coal fines, as the material is so light that floating particles could get directly into the gas stream if not compressed or mixed with another feedstock. Instead, it could be used to supplement other feedstocks that are lower in carbon. If you have coal remnants from industrial process that require difficult disposal, FastOx gasification may provide a unique solution.
Fly ash is essentially a collection of inorganic material with some metals and little to no carbon. Consequently, it does not contribute to the production of syngas. However, adding fly ash will increase the amount of inert stone and recoverable metals produced, which are useful as a construction aggregate material. As such, fly ash can be used as a feedstock component for FastOx gasification but not a feedstock by itself. It is best to blend fly ash with a high-carbon waste stream like municipal solid waste, biomass, or tires.
Evaluating the exact impacts of using fly ash as a component of feedstock requires further information because the mineralogy of fly ash varies based on its origin. Based on typical fly ash compositions, the ratio of fly ash to biomass are likely to fall within a range of 20-40% fly ash to 60-80% biomass by weight. However, a proximate and ultimate analysis of the fly ash in question would need to be conducted prior to a feasibility study in order to determine the optimal ratio.
If you would like more information on these analyses, please contact us and we will gladly provide additional information.
Oli-Based Drilling Mud
Oil-based drilling mud is generally difficult to dispose of because its constituents vary drastically in terms of materials and concentrations.
Sierra Energy would require additional information regarding the composition of a specific mud being considered to determine the carbon content of the mud. This will dictate how much carbon could react in our system and create syngas, heat, and inert stone. It is unlikely that drilling mud would serve as a primary feedstock and would likely need to be mixed with other waste streams.
Through a feasibility study, Sierra Energy can provide a much better sense of how well oil-based drilling mud would work in the FastOx system.