Worldwatch researchers recently completed their initial visit to Jamaica for the Caribbean Low-Carbon Energy Roadmaps project. The team discussed a range of issues related to Jamaica’s energy infrastructure and needs with policymakers and stakeholders, and one issue that stood out was the potential for more cogeneration at sugar mills.
As of 2010, the agricultural sector accounted for 6 percent of Jamaica’s gross domestic product (GDP) and 20 percent of the nation’s employment. The largest of the industries within the agricultural sector – the sugarcane industry – accounted for 35,000 direct jobs and 100,000 indirect jobs. About 46,000 hectares, or nearly 5 percent of Jamaica’s land, is dedicated to growing sugarcane.
But what does this industry have to do with Worldwatch’s Low-Carbon Energy Roadmap in Jamaica? The simple answer is that waste from sugar mills is already contributing to Jamaica’s energy portfolio, and has the potential to play an even more substantial role.
Only about 15 percent of the sugarcane plant’s weight is sugar. Nearly 28 percent of the plant’s weight is bagasse, a cellulose fiber residue and byproduct of sugarcane processing that historically has been incinerated as waste but is increasingly being used as a fuel for cogeneration.
Cogeneration in a sugar mill works by feeding bagasse (or any other fuel) into a boiler. Burning the bagasse produces steam, which drives a turbine that then turns a generator, generating electricity. Excess steam not converted to electricity is circulated through pipes to heat local and on-site buildings, thus giving the process the name of cogeneration.
All major sugar mills in Jamaica use cogeneration today, but the problem lies in the fact that these cogeneration plants are inefficient and do not use all of the bagasse available to them. When these cogeneration plants were built decades ago, they were designed with low efficiencies so as to maximize the amount of bagasse they could incinerate. Demand for sugar was much greater than on-site demand for power and heat, and it was unrealistic at the time for these sugar mills to sell excess electricity to the grid. Given the conditions when these plants were built, it made sense to build less efficient boilers and to simply burn-off the excess bagasse.
Today however, improving the efficiency of bagasse cogeneration provides Jamaica with a tremendous opportunity to help meet its future power demands in a more sustainable manner. Peak load in Jamaica is expected to grow from 680 megawatts (MW) in 2009 to 1500 MW by 2030. A Jamaican government report published in 2010 stated that if all sugar mills were made more efficient and connected to the grid, they could provide it with between 220-300 gigawatt-hours (GWh) per year. Another study suggested that the nation’s recently privatized sugar mills – accounting for 5 of the 7 major sugar mills in Jamaica – could provide the Jamaican grid with up to 94 MW of capacity during the sugarcane harvest season. Making these 5 plants more efficient could reduce Jamaica’s oil imports by 22.3 million gallons per year, as much of the country’s electricity is generated using oil and diesel fuel.
Nevertheless, there are several barriers to connecting Jamaica’s sugar mills to the grid. The first major barrier is that the boilers currently used in the cogeneration plants are less than 50 percent efficient, meaning the plants often do not produce surplus electricity that they can sell to the grid. In order to maximize electricity generation, these boilers will need to be replaced with more efficient boilers. Existing boiler technologies offer efficiencies as high as 88 percent.
Another major barrier to grid connection is the price sugar producers would receive for selling electricity to the grid under current conditions. As mentioned in an earlier ReVolt post, Jamaica recently instituted a net billing policy that allows the Jamaican electricity distribution monopoly to purchase excess locally-generated electricity from consumers for US$0.10 per kilowatt-hour (kWh) and sell electricity back to other consumers for US$0.38-0.40 per kWh. If sugar producers could be guaranteed a higher price for selling electricity to the grid, it would provide them with a much greater incentive to retrofit their bagasse plants.
Finally, the fact that bagasse cannot be used to power these cogeneration plants year round presents another problem. The sugar harvest season lasts about 185 days, so sugar producers need to find another fuel for their cogeneration plants if they are to sell electricity to the grid year round. In Mauritius, a country that has successfully retrofitted most of its sugar mills to deliver electricity to the grid, sugar mills use coal to power their cogeneration plants during the sugarcane non-harvest season. Using coal or any other type of fuel to power the sugar mill cogeneration plants year round in Jamaica could reduce oil imports by an additional 35.3 million gallons per year.
Connecting Jamaica’s sugar mill cogeneration plants to the grid would benefit Jamaica’s sugar industry as well as the environment. The Jamaican sugar industry has been in decline for the past decade; its relatively high production costs make it economically uncompetitive and it is largely due to Preferential Agreements with the European Union that the sugar industry is as strong as it is today. Therefore, the ability to sell electricity to the grid would provide sugar mills with another source of revenue and could help to preserve a traditional Jamaican industry.
Environmentally speaking, it is estimated that by simply introducing more efficient boilers to the 5 recently privatized sugar mills and connecting their cogeneration plants to the grid, Jamaica could avoid 221,844 tonnes of carbon dioxide (CO2) emissions per year. Electricity production from bagasse cogeneration plants also fits well into a future clean energy infrastructure as it complements solar and wind development. While solar and wind are intermittent sources of energy, cogeneration plants at sugar mills can provide a flexible baseload source of power.
If Jamaica can overcome technical and economic barriers to retrofit bagasse cogeneration plants and connect them to the grid, it will be able to strengthen its sugar industry while providing for a cleaner energy future.
Matt Lucky is a Sustainable Energy Fellow at the Worldwatch Institute.