Abstract
AbstractThe use of diesel fuel in crop and transportation operations is responsible for one third of the carbon emissions in sugarcane biorefineries. A possible solution is to replace it with biodiesel from lipids, directly produced from sugarcane by highly productive heterotrophic microalgae. In this study a heterotrophic microalgae biodiesel plant, integrated with a typical Brazilian sugarcane bio‐refinery, was designed and evaluated. Molasses, steam, and electricity from sugarcane processing were used as inputs for microalgae production. For a non‐integrated plant, the production cost of the microalgae biodiesel was estimated at 2.51 and 2.27 $/liter for fed‐batch and continuous processes, respectively. Equipment for cultivation and carbon sources was the highest cost affecting the financial feasibility of the proposed design. For the integrated plant, at present ethanol and biodiesel selling prices, the profitability would be lower than a first‐generation sugarcane bio‐refinery using fossil diesel fuel for its operations. However, the CO2 emissions would be reduced by up to 50 000 × 103 kg per year at a cost of $83 10−3 kg−1 CO2‐eq. If carbon credits are considered, the process becomes economically profitable even at present fuel prices. © 2020 The Authors. Biofuels, Bioproducts, and Biorefining published by Society of Chemical Industry and John Wiley & Sons, Ltd
Highlights
The continuous improvement of sugarcane biorefineries has resulted in a large reduction in greenhouse gas (GHG) emissions and fossil fuel consumption.[1]
We present a techno-economic assessment of the microalgae biodiesel plant based on the conversion of molasses into microalgae lipids
At present fuel prices (~$0.6 L−1 ethanol and ~$0.8 L−1 biodiesel), the integrated plant would be less profitable than a first-generation bio-refinery
Summary
The continuous improvement of sugarcane biorefineries has resulted in a large reduction in greenhouse gas (GHG) emissions and fossil fuel consumption.[1]. Microalgae are regarded as the most productive culture for oil and biomass production, with theoretical yields of up to 40 × 103 kg of oil per hectare per year.[8] On a large scale, the productivity still falls short and capital and energy costs associated with cultivation and harvesting are the main cost drivers.[9] Microalgae can be cultivated under autotrophic or heterotrophic conditions. In the former, light, CO2, and nutrients must be provided for photosynthesis to occur. Closed bioreactors allow for steady conditions throughout the year, regardless of environmental conditions.[16]
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