267438 Distributed Small Scale Marine Biorefineries: Scale Analyses and Design for Developing Countries
Distributed Small Scale Marine Biorefineries: scale analyses and design for developing countries.
Alexander Golberg1, Gregory Linshiz2, Nathan J. Hillson2, J. D. Keasling, M. Koudritsky
1 Department of Mechanical Engineering, Etcheverry Hall, 6124, University of California
at Berkeley, Berkeley, CA 94720 USA. and Center for Engineering in Medicine and Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
2 Joint BioEnergy Institute ,Lawrence Berkeley National Labs, 1 Cyclotron Road, Berkeley, CA 94720.
3 Independent researcher, 2-236 Duke st. W. Kitchener ON, Canada.
4 Independent researcher, Milner 16b Hadera P.B.20995, Israel.
The major growth in liquid fuel demand over the next 20 years will be predominantly due to developing countries. While Gross Domestic Product (GDP) and primary energy production in Organization for Economic Co-operation and Development (OECD) countries is not linearly correlated, GDP growth in developing countries requires increases in primary energy production. The World Energy Council predicts that India and China will overtake developed countries in transportation fuel consumption by 2025. Due to climatic, economic, and fossil fuel resource constraints, there is an urgent need for the sustainable, cost-effective production of carbon-neutral transportation fuels.
Biofuels present an alternative to fossil fuels. First generation biofuel technologies utilize established processes and currently produce biofuels on a commercial scale. First generation feedstocks include sugar beet, starch-bearing grains, and conventional vegetable oil crops, and first generation fuel products include ethanol and biodiesel. Second and third generation biofuel technologies, currently in research and development, utilize animal fat, lignocellulosic biomass, and algae feedstocks, and produce hydrotreated vegetable oil, cellulosic-ethanol, biomass-to-liquids (BtL)-diesel, bio-butanol, and advanced drop-in replacement fuels such as fatty-acid ethyl esters, bisabolene, pinene, n-alkanes, n-alkenes, and methyl ketones.
Although biofuels may collectively supply a portion of future transportation fuel demand, competition between “energy crops” and “food crops” for land and water resources is a growing concern. Furthermore, the extents to which land erosion, potable water consumption, fertilizers, pesticides, and climate change impact biofuel sustainability have yet to be evaluated .
While significant efforts are being directed towards developing feedstocks and conversion technologies, biorefinery design remains in its infancy. The optimization of biorefinery size, feedstock, technology, and serviced area will be required to reduce the costs of the resulting biofuel products.
Recent research in constructal design shows that the optimal distribution of flows of products and services across a populated area depends on a balance between the size of the production centers with sizes of distribution networks that connect these centers to end users. Although larger systems are thermodynamically more efficient in production, they serve larger areas; thus, the collection and distribution logistical costs also increase with size. Therefore, a balance exists between efficiencies of scale, and system distribution losses. This balance has been investigated both for thermodynamics of energy sources and economics of agricultural/biofuel systems. Applications of the balance principle have been demonstrated for the thermodynamical optimization of hot water flow and heating, refrigeration, combined solar power and desalination, and agricultural product processing economics. The balance principle has also lead to proposals for “distributed energy systems” to optimize energy production size and service area.
The goal of this work is to show that the balance between thermodynamic efficiency of system size, collection and distribution is valid for biorefineries. This work also aims to demonstrate that population characteristics, such as density and per capita liquid fuel consumption, play a critical role in the design of biorefinery size, technology choice and serviced area.
We report a model macro algae biorefinery design for midsize towns in low to medium income countries with low liquid fuel consumption per capita. We targeted these populations since the majority of new fuel systems built in future years will serve their growing demands. We focus our model on macro algae, a promising biofuel crop feedstock that does not compete with food crops for arable land or potable water. Furthermore, macro algae, which do not contain lignin, are convenient candidates for cost effective processing with current technology. We analyze biorefinery production of a transportation biofuel from the green macro algae Ulva sp, and demonstrate the integration of this model biorefinery into the distributed energy systems. For example, we analyze a system that would supply all the liquid fuel needs of a 20,000 person coastal town in a middle income country, where the annual per capita demand is 26 gallons of liquid fuel per year. The designed system consists of an open controllable photobioreactor and a consolidated bioprocessing unit, which yields renewable liquid fuel. We propose to use a green seaweed Ulva as a biomass source. The analyses of prior studies shows that Ulva yields of 15-22 kg dry weight∙ m-2 ∙year -1, with a heating value of about 19 MJ∙kg-1, can be achieved with 200 W∙m-2 solar radiation with a zero pesticide footprint. With current ethanol/seaweed conversion rates, a 30 ha cultivation farm, along with 8 ha of a photo-voltaic (PV) facility to provide operational energy, is required to satisfy the liquid fuel demands of a middle income town in a developing country. The system is easy to operate and maintain, and can be manufactured and installed in multiple locations. Finally, in the context of a single biorefinery, we compare macro algae with corn grain and cassava feedstocks.
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