What is Essential to FastOx Gasification?

Sierra Energy focuses on converting non-recyclable trash into energy. Based on that principle, 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.

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 recommended 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.

Reluctant Waste

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:

1. Wet waste
2. Waste with low amounts of carbon
3. Oil-based drilling mud
4. Raw sewage
5. Grey water
6. 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.

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.

Feedstock Size

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 should be approximately 1-3 inches.
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.

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.