Banana waste may find a powerful use in Queensland’s biofutures industry
The Queensland Government has allocated $20 million in funding over the next three years to create a sustainable biofutures industry in the State. The Queensland Biofutures 10-year Roadmap and Action Plan was released last June.
Biofutures refers to the industrial biotechnology and bioproducts sector: the development and manufacturing of products from sustainable organic and/or waste resources, rather than fossil fuels.
The aim is to utilise a number of ‘waste steams’ as feedstocks in the future to generate a wide range of sustainable chemicals, fuels, synthetic rubber, cosmetics, detergents and textiles.
While the most common potential feedstocks mentioned are sugar cane bagasse, sorghum stover, algae and recycled waste/used lube oil, Growcom hopes that other feedstocks such as banana waste from the horticulture industry will be utilised.
More than 30 000 tonnes of bananas are grown in Australia each year, mainly in northern Queensland. About 20 per cent of the banana crop, some 60 000 tonnes a year, is damaged or bruised during harvesting and transport to packing sheds and cannot be sold.
Damaged bananas and banana bunch stalks can be converted into a gaseous fuel by anaerobic digestion, a process in which bacteria break down carbohydrates in the absence of air, producing a mixture of methane and carbon dioxide. In fact, all plant material can be processed in this way.
Several years ago, Growcom was involved in a Banana Waste to Energy project to produce and harvest methane gas from banana waste, funded by the Sustainable Industries Division of the Queensland Environmental Protection Agency (EPA).
This followed a University of Queensland laboratory study in collaboration with the Australian Banana Growers’ Council and Ergon Energy to evaluate the suitability of banana waste as a feedstock for biogass. The study showed that bananas could yield about 204 litres of biogas per kilogram of dry banana with the same energy content as 0.1 litres of diesel fuel. The biogas was of sufficient quality to be used directly as a substitute for diesel in combustion engines, containing about 40 per cent methane and insignificant amounts of hydrogen sulphide and other contaminants. The remaining nutrient-rich solution was suitable for use as fertiliser.
Growcom’s project demonstrated the feasibility of constructing a low-cost on-farm anaerobic digester to convert banana waste to biogas. It also assessed the most productive use of the biogas fuel on-farm to power machinery and return power to the grid.
Infrastructure including a 460 000-litre anaerobic digester with the capacity to process 2500 tonnes of banana waste per year and produce about 85 000 cubic metres of methane was built on a banana plantation at Tully. At this level of output the biogas could be used to continuously generate about 35 kilowatts of electrical power or provide much of the fuel requirements for a fleet of about 100 gas-converted vehicles.
Growcom considers that the amount of waste produced by the Queensland banana industry could sustain the operation of 10 similar-sized digester units. The technology also has the potential to be applied at other fruit packing plants, fruit and vegetable markets and food processing facilities.
The challenge now is to find an investor to undertake some industrial design to enable the system to be commercialised and made available to growers to reduce the energy inputs for their business. The technology could also be marketed and exported to provide a power source for small remote communities in developing countries.
We are hopeful that these developments may now occur with the current encouragement of the Queensland Government in a biofutures industry in this State.