Anaerobic Digestion Feasibility Study of Palm Oil Mill Effluent (POME) in Costa Rica

While the introduction of the African Palm to Costa Rica has done much to reinvigorate the economy, by providing a source of margarine and cooking oil, the effluent at the site of Palm Oil Mills (POME) can have a major environmental impact. Existing treatment in a series of open lagoons at high ambient temperatures, results in the uncontrolled production of methane and carbon dioxide, which are both green house gases (GHGs).

A team including EBL and Bronzeoak Ltd. were funded by the UK Foreign and Commonwealth Office (Climate Change Challenge Fund) to review the potential for implementing an anaerobic digestion programme which would capture the fugitive methane emissions in order to generate electricity or to feed the boilers on site. At the same time the process would reduce the oxygen demand in local water courses by significantly reducing the COD of the effluent.

The report concluded that prospects for a successful commercial programme were very strong and that a typical Palm Oil Mill processing 45t/h of fresh fruit bunches and generating 1,000m3/d of effluent, would have the potential to generate 2.6MW of electricity from the waste.

Anaerobic Digestion plants generate biogas, which is converted to electricity in a combined heat and power (CHP) set, on a farily continuous basis. The value of the gas or electricity produced depends, to a large extent, on the pattern of energy use on site and the feasibility of exporting electricity to the local grid when less power is needed. At one site visited at Coopeagropal most of the energy could be used to substitute local fuel use and would command a premium rate.

Due to the potential for an Anaerobic Digestion plant to mitigate harmful GHG emissions there would be significant potential for the use of Clean Development Mechanism (CDM) funding. Costa Rica is one of the first countries to take advantage of CDM funding for such projects and prospects for POME digestion plants are very promising.