Microalgae are receiving increased global attention as a potential sustainable “energy crop”for biofuel production. An important step to realizing the potential of algae is quantifying the demands commercial‐scale algal biofuel production will place on water and land resources. We present a high‐resolution spatiotemporal assessment that brings to bear fundamental questions of where production can occur, how many land and water resources are required, and how much energy is produced. Our study suggests that under current technology, microalgae have the potential to generate 220 × 109 L yr−1 of oil, equivalent to 48% of current U.S. petroleum imports for transportation. However, this level of production requires 5.5% of the land area in the conterminous United States and nearly three times the water currently used for irrigated agriculture, averaging 1421 L water per liter of oil. Optimizing the locations for microalgae production on the basis of water use efficiency can greatly reduce total water demand. For example, focusing on locations along the Gulf Coast, southeastern seaboard, and Great Lakes shows a 75% reduction in consumptive freshwater use to 350 L per liter of oil produced with a 67% reduction in land use. These optimized locations have the potential to generate an oil volume equivalent to 17% of imports for transportation fuels, equal to the Energy Independence and Security Act year 2022“advanced biofuels”production target and utilizing some 25% of the current irrigation demand. With proper planning, adequate land and water are available to meet a significant portion of the U.S. renewable fuel goals.
biomass
The U.S. Department of Energy (DOE) is promoting the development of ethanol from lignocellulosic feedstocks as an alternative to conventional petroleum-based transportation fuels. DOE funds both fundamental and applied research in this area and needs a method for predicting cost benefits of many research proposals. To that end, the National Renewable Energy Laboratory (NREL) has modeled many potential process designs and estimated the economics of each process during the last 20 years. This report is an update of the ongoing process design and economic analyses at NREL. We envision updating this process design report at regular intervals; the purpose being to ensure that the process design incorporates all new data from NREL research, DOE funded research and other sources, and that the equipment costs are reasonable and consistent with good engineering practice for plants of this type. For the non-research areas this means using equipment and process approaches as they are currently used in industrial applications. For the last report 1, published in 1999, NREL performed a complete review and update of the process design and economic model for the biomass-to-ethanol process utilizing co-current dilute acid prehydrolysis with simultaneous saccharification (enzymatic) and co-fermentation. The process design included the core technologies being researched by the DOE: prehydrolysis, simultaneous saccharification and co-fermentation, and cellulase enzyme production. In addition, all ancillary areas feed handling, product recovery and purification, wastewater treatment (WWT), lignin combustor and boiler-turbogenerator and utilities were included. NREL engaged Delta-T Corporation (Delta-T) to assist in the process design evaluation, the process equipment costing, and overall plant integration. The process design and costing for the lignin combustor and boiler turbogenerator was reviewed by Reaction Engineering Inc.
This paper examines the possibilities of breaking into the cellulosic ethanol market in south Louisiana via strategic feedstock choices and the leveraging of the area’s competitive advantages. A small plant strategy is devised whereby the first-mover problem might be solved, and several scenarios are tested using Net Present Value analysis.
This paper introduces a spatial bioeconomic model for study of potential cellulosic biomass supply at regional scale. By modeling the profitability of alternative crop production practices, it captures the opportunity cost of replacing current crops by cellulosic biomass crops. The model draws upon biophysical crop input-output coefficients, price and cost data, and spatial transportation costs in the context of profit maximization theory. Yields are simulated using temperature, precipitation and soil quality data with various commercial crops and potential new cellulosic biomass crops. Three types of alternative crop management scenarios are simulated by varying crop rotation, fertilization and tillage. The cost of transporting biomass to a specific demand location is obtained using road distances and bulk shipping costs from geographic information systems. The spatial mathematical programming model predicts the supply of biomass and implied environmental consequences for a landscape managed by representative, profit maximizing farmers. The model was applied and validated for simulation of cellulosic biomass supply in a 9-county region of southern Michigan. Results for 74 cropping systems simulated across 39 sub-watersheds show that crop residues are the first types of biomass to be supplied. Corn stover and wheat straw supply start at $21/Mg and $27/Mg delivered prices. Perennial bioenergy crops become profitable to produce when the delivered biomass price reaches $46/Mg for switchgrass, $118/Mg for grass mixes and $154/Mg for Miscanthus giganteus. The predicted effect of the USDA Biomass Conversion Assistance Program is to sharply reduce the minimum biomass price at which miscanthus would become profitable to supply. Compared to conventional crop production practices in the area, the EPIC-simulated environmental outcomes with crop residue removal include increased greenhouse gas emissions and reduced water quality through increased nutrient loss. By contrast, perennial cellulosic biomass crops reduced greenhouse gas emissions and improved water quality compared to current commercial cropping systems.
When the lignocellulosic biofuels industry reaches maturity and many types of biomass sources become economically viable, management of multiple feedstock supplies – that vary in their yields, density (tons per unit area), harvest window, storage and seasonal costs, storage losses, transport distance to the production plant – will become increasingly important for the success of individual enterprises. The manager’s feedstock procurement problem is modeled as a multi-period sequence problem to account for dynamic management over time. The case is illustrated with a hypothetical 53 million annual US gallon cellulosic ethanol plant located in south west Kansas that requires approximately 700,000 metric dry tons of biomass. The problem is framed over 40 quarters (10 years), where the production manager minimizes cumulative costs by choosing the land acreage that has to be contracted with for corn stover collection, or dedicated energy production and the amount of biomass stored for off-season. The sensitivity of feedstock costs to changes in yield patterns, harvesting and transport costs, seasonal costs and the extent of area available for feedstock procurement are studied. The outputs of the model include expected feedstock cost and optimal mix of feedstocks used by the cellulosic ethanol plant every year. The problem is coded and solved using GAMS software. The analysis demonstrates how the feedstock choice affects the resulting raw material cost for cellulosic ethanol production, and how the optimal combination varies with two types of feedstocks (annual and perennial).
Fast-growing, oil-producing species of microalgae have become the focus of attention for both biomass and biodiesel biofuels, but questions remain about scalability, economics, and the competition between large-scale microalgae cultivation and agriculture, with regard to water, fertilizer, and land use. By cultivating microalgae on domestic wastewater, the water and fertilizer problems can be overcome, and by using algae for improved wastewater treatment, economic and environmental benefits can be realized. Land use for traditional large-scale algae cultivation systems, open ponds and closed photobioreactors (PBRs), continues to be a formidable challenge, however.
Assuming that algae production must be linked to existing wastewater treatment facilities and given that these facilities are deeply embedded in urban infrastructure, the integration of algae production into exiting urban infrastructure is both prohibitive in cost and unrealistic to implement. Alternatively, installing algae production in remote locations at great distances from the wastewater facilities requires significant investments in pipelines and transport infrastructures as well as in energy for pumping water and delivering materials. Could the solution for a practical and affordable large-scale algae production system, linked to wastewater treatment be located offshore, at least for coastal cities?
We propose a system called OMEGA (Offshore Membrane Enclosures for Growing Algae), consisting of floating photobioreactors (PBRs) made of flexible plastic sheets welded into a series of interconnected chambers. The modular PBRs are attached to each other to form a system that is attached to moorings or tethered to piers. If necessary, the system is protected by a breakwater.
The OMEGA PBRs are filled with secondary-treated wastewater redirected from established outfalls and inoculated with oil-producing freshwater algae. Nearby Power Plants or other sources of fossil fuel combustion provide CO2 to stimulate algae growth. Unlike land-based PBRs, which require significant energy input for mixing and temperature control, OMEGA uses surface waves for mixing and the heat capacity of the surrounding water for temperature control. The salinity difference between wastewater and seawater is used for forward osmosis, which 1) concentrates nutrients in the wastewater, stimulating algae growth; 2) dewaters the algae, facilitating harvesting; and 3) cleans the wastewater released into the surrounding environment. If the cultivated freshwater algae accidentally escape into the surrounding, seawater they pose no threat to the marine environment, as they cannot survive in saltwater.
While the proposed OMEGA system overcomes many of the difficulties inherent in existing land-based algae cultivation, there remain long-standing challenges in biology, engineering, environmental impact, and politics. Some of these challenges are associated with algae cultivation in general (e.g., growth control, grazers, pathogens, and dewatering) and others with OMEGA in particular (e.g., materials, permitting, fouling, marine mammals). These issues and others are under investigation as part of an OMEGA feasibility study supported by grants from NASA ARMD and the California Energy Commission. The purpose of this paper is to evaluate if indeed the future of algae biofuels is offshore?
Meeting the Energy Independence and Security Act (EISA) renewable fuels goals requires development
of a large sustainable domestic supply of diverse biomass feedstocks. Macroalgae, also known as
seaweed, could be a potential contributor toward this goal. This resource would be grown in marine
waters under U.S. jurisdiction and would not compete with existing land-based energy crops.
Very little analysis has been done on this resource to date. This report provides information needed for an
initial assessment of the development of macroalgae as a feedstock for the biofuels industry.
The findings suggest that the marine biomass resource potential for the United States is very high based
on the surface area of the marine waters of the U.S. and rates of commercial macroalgae production in
other parts of the world. However, macroalgae cultivation for fuels production is likely a long term effort.
Analysis of the available data showed that considerable scale up in cultivation over current world-wide
production and improvements in processing throughout the supply chain are needed.
Despite the high resource potential, the United States does not currently have a macroalgae production
industry and would have to develop this capability. In order to meet current renewable fuels goals, the
scale of the effort would have to be high in comparison with activity in other parts of the world. For
example, replacing 1% of the domestic gasoline supply with macroalgae would require annual production
rates about ten and one-half times current worldwide production. This could be accomplished through
cultivation on 10,895 km2 of ocean surface, based on current rates of production reported for the
international macroalgae cultivation industry. Advances in cultivation technology already being tested
could potentially increase production from three to ten fold with a corresponding decrease in the area
needed for cultivation to meet specified production goals. While it is no surprise that the cost estimates to
produce fuel from macroalgae are currently high, it should be noted that this is based on a limited amount
of available data and that production costs for macroalgae can benefit from increased efficiency and scale.
A thorough analysis is warranted due to the size of this biomass resource and the need to consider all
potential sources of feedstock to meet current biomass production goals. Understanding how to harness
this untapped biomass resource will require additional research and development. A detailed assessment
of environmental resources, cultivation and harvesting technology, conversion to fuels, connectivity with
existing energy supply chains, and the associated economic and life cycle analyses will facilitate
evaluation of this potentially important biomass resource.
This paper summarizes some of the major impacts rapid growth in the corn
based ethanol (CE) production is now having on infrastructure in the Midwestern corn
producing states and examines some of the likely infrastructure needs that might be
expected to occur as a consequence of the future development of biomass based ethanol (BE) production
The National Renewable Energy Laboratory (NREL) originally developed this application for biopower with funding from the Environmental Protection Agency's Blue Skyways Collaborative. The Department of Energy's Office of Biomass Program provided funding for biofuels functionality. More information on funding agencies is available: http://www.blueskyways.org and http://www.eere.energy.gov/biomass/.
The purpose of this study is to analyse the economical and environmental performance of switchgrass and miscanthus production and supply chains in the European Union (EU25), for the years 2004 and 2030. The environmental performance refers to the greenhouse gas (GHG) emissions, the primary fossil energy use and to the impact on fresh water reserves, soil erosion and biodiversity. Analyses are carried out for regions in five countries. The lowest costs of producing (including storing and transporting across 100 km) in the year 2004 are calculated for Poland, Hungary and Lithuania at 43–64 € per oven dry tonne (odt) or 2.4–3.6 € GJ−1 higher heating value. This cost level is roughly equivalent to the price of natural gas (3.1 € GJ−1) and lower than the price of crude oil (4.6 € GJ−1) in 2004, but higher than the price of coal (1.7 € GJ−1) in 2004. The costs of biomass in Italy and the United Kingdom are somewhat higher (65–105 € odt−1 or 3.6–5.8 € GJ−1). The doubling of the price of crude oil and natural gas that is projected for the period 2004–2030, combined with nearly stable biomass production costs, makes the production of perennial grasses competitive with natural gas and fossil oil. The results also show that the substitution of fossil fuels by biomass from perennial grasses is a robust strategy to reduce fossil energy use and curb GHG emissions, provided that perennial grasses are grown on agricultural land (cropland or pastures). However, in such case deep percolation and runoff of water are reduced, which can lead to overexploitation of fresh water reservoirs. This can be avoided by selecting suitable locations (away from direct accessible fresh water reservoirs) and by limiting the size of the plantations. The impacts on biodiversity are generally favourable compared to conventional crops, but the location of the plantation compared to other vegetation types and the size and harvesting regime of the plantation are important variables.