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On-going projects

THYME: Refuel

Next generation solid fuels

The
Challenge

To achieve zero carbon targets and build sustainability into energy production, society is increasingly moving to bio renewable feedstocks as a replacement for fossil fuels as part of the renewables mix. Currently, woody biomass is the dominant feedstock for bioenergy production via combustion, leading to increased demand and costs as well as wider concerns about sustainability.

Lignocellulosic crops such as straws produce abundant supplies of dry waste plant matter (biomass) which can be used as renewable feedstocks for energy production.  However, they contain a high proportion of non-carbon components, which, during the energy production process leaves residues in the form of ash that can clog and corrode reactors leading to a need to temporarily shut down, clean and reset plant operations. 

field
11.3% of UK energy production is from biomass derived operations, 2019 ONS

These stoppages and the corrosive qualities of some of the inorganic deposits radically decrease the lifespan of a reactor. Both factors have a major effect on the efficiency and sustainability of waste to energy plants, with a knock-on effect on the cost of this form of electricity production.

The
Approach

Lead researchers

Vasiliki Skoulou Martin Taylor

Project funded by

Project partners

Dr Peter Hurst - Biorenewables Development Centre

Simon Walker - Jesmond Engineering

The team examined the pre-treatment of various lignin sludges produced from waste streams of the bioethanol process, as a means of converting them to alternative solid fuels.

The focus was on investigating the effect of leaching on the removal of problematic ash constituents. Leaching is a known pre-treatment for coal, involving the use of demineralised water to wash the material under specific conditions, in order to remove problematic materials such as Potassium, Chlorine, Sodium and Sulphur, among others.

The researchers found that leaching successfully optimised the quality of these sludges by removing between 60-80% of undesirable ash components. Sugar deficient sludges from barley straw, wheat straw and bagasse were found to have a higher calorific value and usability than their equivalent raw waste streams.

The research confirmed conventional water leaching as a relatively cheap and scalable technology that could be implemented by bioenergy producers. 

Following the success of the original THYME funded collaborative project, the partners successfully bid for THYME Follow-on Funding to optimise these next generation fuels in the form of de-ashed powder and pellets to ensure they meet industrial quality standards and are suitable for usage in industrial scale systems. 

The optimised pellets will be tested under thermochemical (pyrolysis/gasification) conditions to study their bioenergy production potential. An evaluation will be made of solutions to potential operational issues, so that pellets of this type can be used in industrial scale fixed or fluidised bed systems.

 

The Impact

Herbaceous biomass such as straws sequester carbon dioxide during their growing cycle, which is then released during energy production, making them a near carbon neutral energy source. Fast growth cycles and adaptability to different environments makes them ideal replacements for imported wood pellets, which are common feedstocks for bioenergy production.

By using underutilised waste streams, such as sludges from bioethanol production, we can ensure we extract as much energy as possible from these feedstocks rather than leaving the wastes to decompose in the environment.

This research provides alternative candidates for the next generation of solid fuels that can be used to diversify current biomass feedstocks, broadening the market and making the waste to energy process far more sustainable.

The research has the potential to improve the efficiency of bioenergy production facilities and diversify usable feedstocks by significantly reducing ash build up and the associated facility downtime, thereby lowering energy production costs and increasing their viability against traditional fossil-fuel production.  

Other on-going research projects