The potential for seaweed as a replacement fuel for combustion in sugar cogen power plants

The Government of Mauritius has introduced energy policies to reduce the use of fossil fuels in response to global heating. Electricity from renewable sources mainly generated for the island by sugar cane factories through cogeneration. The approach uses bagasse during the sugar-cane crop season and coal during the off-crop season to feed the boilers of their power plants. With an annual decrease in sugarcane production, due to field abandonment by planters, coupled with an increase in coal import prices and electricity demand, there is an urgency to compensate for this fuel deficit. In this context, “Sargassum sp” - a common seaweed washed up along the coastline was assessed as a potential bioenergy substitute. Currently Sargassum is a waste material regularly cleared from public beaches and hotel fronts and dumped in rudimentary landfill sites. The study undertook an analysis of the fuel and chemical characteristics of Sargassum in pure form as well as in comixed half ratios with coal and bagasse. Then, the technical feasibility of integrating a pre-treatment model for the seaweed into an existing bagasse process line at a power station was studied by developing a functioning pilot mechanical processing plant. The analytical results indicated a low calorific value of 12.9MJ/Kg, although this was comparable to other biomass resources. The dry mass was only 26.6% which would make Sargassum unfavourable towards direct combustion without pre-treatment. Alkali metals, found in the dry ash, could cause boiler corrosion and fouling. Therefore, there are challenges in the use of seaweed for power generation. The pilot plant was able to take in fresh Sargassum and treat it to produce feedstock for the power station. Future research (LCOE, Sensitivity Analysis) on the economic viability of integrating Sargassum into existing boiler feed lines for the power station will be undertaken.