Alternative Fuels — a sticky issue or growing opportunity?

Across Europe the use of alternative fuels continues to provide significant opportunities for low carbon energy production and the circular economy. And the range of fuels is growing. Today we see biomass fuels spanning forestry and wood fibres, specialist crops and agricultural waste, to meat and bone meal (MBM), even processed sewage sludge.

Waste as alternative fuel is also increasing. Waste based fuels have been around for a while but it is Refuse Derived Fuel (RDF) and Solid Recovered Fuels (SRF) where the focus is growing.

The energy generation landscape is changing too. The number of dedicated Biomass energy plants including new build or conversion, have now reached quite significant numbers, some 30 sites in the UK alone, with more in construction. Gasification plants burning RDF and SRF are also on the rise.

For energy hungry industries, in particular the Cement sector, alternative fuels to co-fire or replace existing fossil fuel systems are also popular. While Germany leads the European market there is still plenty of opportunity to increase co-firing across the board with the potential to cut CO2 emissions by millions of tonnes in this industry alone.

However, if you are thinking alternative fuels, think carefully, as there are potential issues, especially for storage and materials handling. All of the products mentioned share similar characteristics in that they are non-free flowing. They can be wet, sticky and non-homogenous. They are liable to compact and will happily form bridges in silos and chutes. So the potential to disrupt downstream processes shouldn’t be underestimated.

Material characteristics can change too, delivery to delivery, and we frequently see over-optimistic expectations when it comes to feedstock quality and consistency.  Even a reasonably consistent input material like waste wood can throw-up surprises. One in ten truck loads for example may be largely or completely composed of fine dust. Others may be black and compacted having been stored too long. RDF with mixed organic residues can be even more challenging. These factors may be outside your control and will test the capabilities of installed handling systems if the design is defective, resulting in poor or erratic material flow, stagnant product and costly periods of outage.

Upfront design considerations and proven technologies are crucial here. The temptation to select cheaper ‘equivalent’ but unproven handling solutions will of course be attractive if CAPEX expenditure can be reduced, but makes no sense if the result is higher operational costs to resolve fuel feed issues, with expensive manual interventions and costly fixes. All too typical in our experience.

Design direction to provide sufficient fuel storage, plus reclaim and conveying systems, will also be dictated by site constraints and available space, a factor that is sometimes overlooked at the early stages of project development. Permitted vehicle movements including delivery hours and weekend working will also determine storage requirements and truck reception systems, and there may be environmental factors at play, including noise, dust and water run-off to consider.

Whether you are processing fuel onsite or relying on shipments from third parties fuel cleanliness may also be important with a requirement for oversize and undersize screening and metal removal. Weighing and sampling might also be required to monitor quality and deliver fuel at precise rates to the combustion process. Together with reception systems, storage systems and reclaim conveyors, these are elements that need to work together seamlessly, and for the life of the facility.  

Key technologies for handling and storage should revolve around activated surfaces and ‘first in, first out’ principles. This limits the opportunity for fuel to degrade and for most materials some form of Sliding-Frame or Push-Floor system is advisable. These make for dynamic rather than static storage and ensure that easily-compacted materials are kept on the move.

Other options for enforcing ‘first in, first out’ include hydraulic rotors and tube feeders and in general terms, a system design that favours vertical rather than inclined surfaces, broad rather than narrow channels and positive handling options such as screw-feeders and chain conveyors minimises problems.

Alternative fuels by their very nature will remain a sticky issue, but at the same time a golden opportunity for many. Storage and handling systems are crucial and there is clearly a learning process in play, with fewer plant failures, as operators increasingly focus on operational costs and plant availability rather than tempting but sometime ill-founded CAPEX savings.

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