Deep in the Mekong Delta of South Vietnam a small bio-refinery is converting seaweed into protein, fuel-blendable alcohol, and a bacterial soil product. It is part of a bio-economy demonstration that is also enhancing shrimp quality and yield by co-cropping naturally-occurring aquatic plants as a bio-chemical feedstock.
The project is a collaboration between the Vietnam Academy of Science and Technology (VAST) Institute of Tropical Biology (ITB) and Algen Sustainables. It was funded in part by grants from the governments of Denmark and Netherlands with additional research support from labs in the USA and China.
Algen Sustainables is an international project developer based in the USA. It utilizes macro-algae and other sustainable biomass types in the production of industrial bio-products.
The project sponsors are looking for an industrial partner that can help scale up the technologies to serve the regional chemicals market.
There are over 350,000 hectares of brackish water ponds in the Mekong Delta, most of which are owned by subsistence farmers who use no energy, nutrient, or probiotic inputs. Survival rate of shrimp fry is typically less than 10%. The project team discovered that certain seaweed varieties appear naturally in the ponds and serve as a food source for the shrimp while also clarifying the water. But with growth rates reaching 15% per day during the peak winter season, farmers were concerned that the plants can rapidly cover a pond and pollute it after dying.
The project team began teaching the farmers how to manage the seaweed as a crop, including thinning it when appropriate to maintain rapid but controlled growth. The excess seaweed is now collected by the farmer, dried, and used to make industrial products.
According to Dr. Hoang Nghia Son, Director of ITB, the project highlights the quality and flexibility of research capability in Vietnam. “We are developing entirely new industrial biomass sources, and finding sustainable uses for material others consider waste. Farmers participating in our pilot are enthusiastic about the potential.”
Seaweeds have a tough cell structure. The project is using traditional acid/enzyme treatment to isolate cellulosic sugars, which are then fermented to produce ethanol or other chemicals. Fermentation residuals are used to cultivate micro-organisms that renovate depleted soil. A new addition to the process will extract the plant’s protein for sale to feed producers.
The conversion facility itself is in a standard shipping container that can be moved near biomass sources of interest. It has a rotary tumbler, primary 200 litre fermenter, secondary inoculum fermenter, centrifuge, and two distillation columns. A small amount of electricity from the local grid is used to drive pumps. The heat source for hydrolysis, fermentation, and distillation is a low-emission rice husk boiler, supplemented by a roof-mounted solar water heater. Gravity feed is used to move material down the conversion pathway. Freshwater is recycled, and non-toxic waste water is treated in a shallow pond before release into the environment. Carbon Dioxide from fermentation can be captured and bottled for sale as a co-product.
Says Dr. Son; “Transportation of biomass is expensive, so we had to prove that a self-contained, small batch design could operate close to the farmers. Our pilot facility was engineered to maximize resource recycling, minimize energy consumption, and leave almost no environmental footprint. It was designed and constructed in Vietnam with local labor and equipment.”
Consultants from Netherlands-based Biomass Technology Group (BTG) and UK-based ProForest evaluated the seaweed-to-ethanol pathway in November 2012 as part of developing a draft aquatic biofuel standard. The study was supported by NL Agency, and concluded that scaling it up could offer substantial socio-economic benefits to the communities involved. According to Martijn Vis of BTG; “Vietnam has demonstrated the principle of a novel sustainable bio-refinery pathway for aquatic biomass, which is a pioneering work that contributes to the emerging global bio-economy”.
During 2013 the project will begin collecting rice straw from farmers, the burning of which contributes to Vietnam’s greenhouse gas emissions. Lab work is underway testing various ionic liquid and organic solvent formulations for use in converting the rice straw cellulose and hemicellulose into chemicals like furfural.
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