The use of boilers is the most obvious cogeneration scheme which food/beverage processors might think about. However, biogas converters are another possibility – in which an agrifood business’s organic-rich effluent or waste is converted via anaerobic digestion to methane for use in burners and generators, etc
Where such schemes might previously have been considered for idealistic reasons, they are rapidly becoming more economic as fuel and electricity prices (and effluent disposal rates) rise. Carbon credits are an additional, though bureaucracy-bound, potential income stream.
Grahame Thompson, business development manager for Talbot Green Energy of South Africa, says one ton of chemical oxygen demand (COD) digested produces the equivalent of 350N cu metres of methane and 0.15MW of power.
Talbot Green Energy concentrates on medium/larger industrial projects. For smaller, more do-it-yourself projects, Biogas Power of KwaZulu-Natal, South Africa, has built up a large body of knowledge – particularly on agricultural projects and and dairies and piggeries – over the past five years.
It is important, says Shelby Tyne, a co-founder of Biogas Power, that a biogas digester should not cost too much so that the payback period is not too long.
For instance, on Biogas Power’s first farm project, the cost of the biogas digester was $28,000, compared with an estimated $350,000 which an overseas-technology installation would have cost.
More recently, he says, a South African farmer with 250 cows was quoted $800,000 by a US consultancy for a biogas installation. This would have resulted in far too long a payback period for an operation of that size.
Biogas Power is able to install at lower prices, he says, because it uses own-designs and locally-sourced inputs. Its designs are based on well-established Indian biogas technology.
Biogas Power’s technology is based around a patented "biobag" – basically, a flexible digester bag, which makes the system safer. In the event of methane build-up (which could result in an explosion), the methane is released.
Currently, his company has about 10 farm consulting projects, every one of which has different needs, he says. One farm may require electricity, another may need heating for boilers to produce hot water for sterilisation, etc.
But not only agri-companies which are producing litter should consider installing biogas converters. Any company which has organic material as a by-product should, because any organic material can be digested, with the right bacteria.
This includes abattoirs (digesting offal), canneries, potato chip factories, cheese factories (using whey), factories with animal bone as a by-product, etc.
Many of these projects would be economic immediately, says Tyne. For instance, he estimates a ”starter pack” for a whey digester could cost less than $10,000.
High ”transaction costs” (mainly costs of applying) mean that carbon credits (Cleaner Development Mechanism (CDM) funding) are uneconomic for any facility smaller than a medium-sized brewery. However, where there is a common link between a set of smaller companies – for instance, a common owner – carbon credits are an attractive possibility.
Tyne: Tel 031-7811981 or 083-6428229; email@example.com
Talbot Green Energy: 033-346-1444; firstname.lastname@example.org
AGAMA Energy, Greg Austin: Tel +27-21-7013364; Greg Austin: Tel +27-21-7013364; email@example.com
For additional overseas suppliers of biogas technology, search for “biogas” on on www.foodprocessingafrica.com (subscription required).
For more on carbon credits and biogas converters, search on www.foodprocessingafrica.com