Among renewable sources of energy, the sustainable use of residual biomass for energy production, in particular through gasification processes, represents an important opportunity to achieve the European goals of decarbonization and sustainable growth. Small-scale gasification and cogeneration with biochar production, despite being less popular and deployed than photovoltaics and wind power, offers several benefits over traditional renewables, such as reduced land use, carbon sequestration, and dispatchable generation.
If we look up the word gasification in the dictionary, its definition would be:
“process that converts a fuel, solid or liquid, in a gaseous mixture which can be used as a fuel or for chemical synthesis.”
To be more specific, gasification is a thermochemical degradation process that occurs at high temperature (800-1000 °C) in an environment where the amount of oxygen is lower than that required for a complete combustion. Under these conditions, it is possible to convert a solid fuel into a synthesis gas (syngas) still having a combustion potential; the unburned gas is then piped away to burn elsewhere as needed. When referring to biomass as the original solid fuel, we can more appropriately speak of bio-Syngas.
The gasification process consists of several stages, which lead to the transformation of the carbon material into syngas:
- Drying process: evaporation of the water contained in the biomass.
- Pyrolysis: the material is converted to gas, water vapour (H2O), organic liquids (TAR), char.
- Combustion: oxidation of char to CO and CO2.
- Reduction: formation of combustible gases such as CO and H2.
GASIFICATION VS COMBUSTION
Among the stages that make up the gasification process, there is also a combustion stage. It is only an intermediate step, necessary to release the heat required by other chemical reactions to start the process of generating syngas. Therefore, this is not to be confused with what is commonly referred to as biomass combustion, in other words the burning process of a solid fuel releasing pollutant such as particulate matter and waste residual by-products.
Gasification, in fact, appears to be a cleaner process than combustion: due to the reduced supply of oxygen, combustion is limited to the generation of the heat required to sustain the process and the production of syngas, resulting in no direct emission of particulate matter and other pollutant, such as nitrogen oxides (NOx) and sulphur oxides (SOx). On top of that, gasification shows higher efficiency than combustion in terms of conversion rate between primary energy (biomass, for example) and the overall available energy at the end of the process. In a combustion process, the energy is first transformed into heat and then into electric – and possibly also thermal – power, with an often remarkable energy loss in the first phase. Gasification reduces the dispersion of thermal energy and results in an overall more efficient conversion ratio, although through more sophisticated and challenging processes. RESET, following its mission of environmental sustainability and technological innovation, has chosen gasification for the development of SyngaSmart technology, by designing an original reactor and developing a technological system capable of recovering almost all the energy introduced with biomass.
Biomass plants transform the energy content of biomass into other forms of energy such as heat, in case of combustion process, or other energy carriers:
- Syngas in gasification plants;
- Biogas o biomethane from anaerobic digestion;
- Bio-liquids or bio-oils from pyrolysis plants;
- Carbon or other solid fuels from torrefaction processes or carbonization.
SyngaSmart is a patented technology for biomass micro-cogeneration. It is based on an original fixed bed downdraft gasification process that first turns solid biomass into bio-syngas, and then uses it to generate electricity and heat through a normal stationary engine. The only by-product of the process is represented by biochar, whose properties as a soil improver and carbon sequestration and CO2 reservoir option is now internationally acknowledged, as recently published also by the IPCC.
WHAT BIOMASS CAN BE USED IN A SYNGASMART PLANT?
SyngaSmart plants were originally designed to be powered by woodchips. Throughout the years, RESET’s R&D team has been testing also ‘low quality’ biomass, starting from wood waste (for example, driftwood from rivers and dams, or end-of-life pallets), digestate, organic waste and sewage sludge, verifying and measuring their usability. The application of SyngaSmart technology to such waste biomass offers an unprecedented alternative to business-as-usual solutions like landfill disposal or incineration, creating a positive circular economy process that allows to significantly reduce not only the GHG emissions caused by traditional systems, but also the environmental impacts related to transport emissions, as well as offering an opportunity to generate economic returns.
Currently, it is possible to process biomass such as:
- Woodchips and briquetted wood waste;
- Chopped and briquetted green cutting, prunings and branches;
- Shells from almond, walnuts, hazelnuts, coconuts, coffee husk…
- Agrifood industry waste, composted organic waste, digestate and sewage sludge, through an appropriate pre-treatment process.