AS Guyana moves to become a green state, the National Agricultural Research and Extension Institute (NAREI) is seeking to expand bioenergy opportunities in Guyana to advance sustainable development. The agency has been conducting research to ascertain technologies that could provide Guyanese, particularly those in the agriculture sector, with clean alternative energy.
One area of study is the transformation of sugarcane by-products such as molasses and bagasse into alternative energy. Sugarcane is one of the most promising agricultural bioenergy sources in Guyana. The sugar industry cultivates about 50,000 hectares of the 1.74 million hectares of land being used for agriculture (Thomas, 2015).
As of June 2016, cane sugar is being produced and processed on six estates (Skeldon, Albion, Rose Hall, Blairmont, Enmore and Uitvlugt) along Guyana’s coastal region that produced 227,727 tonnes of sugar in 2015 (Ministry of Agriculture, 2015). The four major by-products of the sugarcane industry are cane tops, bagasse, filter mud and molasses. The bioenergy potential derived from molasses and bagasse are of interest.
Molasses is a dark coloured, viscous liquid remaining after the crystallisation of sugarcane juice. It can be used to produce ethanol through the two-stage process of fermentation and distillation. Ethanol is a colourless volatile flammable liquid, which is produced by the natural fermentation of sugars; alcohol.
The purity of the ethanol can be enhanced by further dehydration as exemplified at Guyana Sugar Corporation (GuySuCo)’s Bioethanol Plant located at Albion Sugar Estate, East Berbice-Corentyne.
It was built that for every 10 tonnes of sugar produced, approximately four tonnes of molasses is generated (Yadav and Solomon, 2006). Annual sugar production stood at 227,727 tonnes with approximately 91,090 tonnes of molasses in 2015.
Using the parameters of the existing bioethanol plant at Albion that has the capacity to produce 1,000 liters of ethanol per day at a rate of 250 litres per tonne of molasses, if all 91,090 tonnes of molasses from annual sugar production is utilised a total of 143,234 barrels of ethanol can be generated annually. Pimentel and Patzek (2005) explained that ethanol has about two-thirds the energy of gasoline therefore 1.52 gallons of ethanol is needed to replace the energy in one gallon of gasoline, hence maximum ethanol production can save Guyana 94,233 barrels of gasoline annually.
Bagasse is the fibrous remains of the cane stalk after crushing and extraction of the juice. It is made up of fibres, water and small quantities of sugar. Mill-run bagasse contains 50.0 per cent fibre, 48.0 per cent moisture and 2.0 per cent soluble solids (Ramjeawon, 2008). For every tonne of sugarcane crushed, a sugar factory produces 0.1 tonnes of sugar and nearly 0.3 tonnes of wet bagasse (Yadav and Solomon, 2006).
Bagasse is usually burnt to heat boilers for the generation of steam and power to operate the sugar factory. If gasified, the net calorific value of the mill-run bagasse is around 8,000 kJ /kg (Ramjeawon, 2008). Guyana’s annual sugar production of 227,727 tonnes generates approximately 683,181 tonnes of bagasse. This can produce approximately 5,465,448,000MJ (5.18×1012 BTU) of energy annually. Such plants can capture between 75 and 80 per cent of the energy in the biomass with an average of 77.5 per cent efficiency (Akay and Jordan, 2011) consequently 4.0147×1012 BTU of energy will be harnessed, hence approximately 695,787 barrels of diesel could be replaced.
CHALLENGES AND OPPORTUNITIES
In an interview with GuySuCo’s Operations Manager and Chief Research Scientist, it was found that ethanol is not being produced at a maximum since the commissioning of the Bioethanol Plant in Albion, Berbice.
The major challenges limiting production are the small capacity of the plant and the small percentage of molasses used for ethanol production. Currently, only about five per cent molasses is generated by the Albion Estate that is being used to produce ethanol.
A major challenge is that molasses is more profitable being sold as is than utilised in ethanol production and this must be factored into the feasibility. GuySuCo has binding agreements with the Demerara Distillers Limited (DDL) and other regional markets for the supply of molasses. There is not enough molasses to expand ethanol production after fulfilling these contractual agreements, hence there has been no plans to have ethanol available to consumers. With moves being made to diversify the sugar industry, ethanol production will remain stagnated, since GuySuCo’s plan is to continue to operate only three estates.
The bioethanol demonstration plant serves to prove the applicability of this technology in Guyana. However, there are ongoing collaborations with neighbouring Brazil to obtain ethanol-powered engines for GuySuCo vehicles. Upon the agreement of all stakeholders, ethanol production can be boosted at the demonstration plant and be used to power GuySuCo’s vehicles with 100 per cent ethanol.
All the ethanol currently produced is used within GuySuCo labs for sanitation purposes and in gasoline blends for the Ministry of Agriculture vehicles. With the sugar industry being diversified to include aquaculture, there is the expectation that ethanol would be used to power the production cycle.
Using GuySuCo’s lands for the cultivation of energy crops is an option, there are long-term (17 years) research projects in progress to experiment on energy canes which are low in sugar, high in biomass and fast growing. Accompanying these research projects are plans for cogeneration using the bagasse.
The use of bagasse in the sugar industry is sustainable since it is used in cogeneration to produce steam for the boilers. The Skeldon Sugar Factory houses a cogeneration plant which supplies 10 MW of power to the national grid during the crop cycle.