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The DOE-OBP Multi-year Program Plan (MYPP) biomass production targets are 44 million dry tons per year by 2012 and 155 million dry tons per year by 2017 (EERE Biomass Program, 2011). Macroalgae, more commonly known as seaweed, could be a significant biomass resource for the production of biofuels. The overall project objective is to conduct a strategic analysis to assess the state of macroalgae as a feedstock for biofuels production. To this end, this project provides an assessment of the potential for domestic macroalgae production and identifies the key technical issues associated with the feasibility of using macroalgae resources. Work began in FY10 as a screening analysis of the key questions related to the status of macroalgae as a feedstock resource. These efforts addressed the state of technology, types of fuels possible, a rough order-of-magnitude resource assessment, and preliminary high-level economic analysis, resulting in a Summary Report entitled Macroalgae as a Biomass Feedstock: A Preliminary Analysis (PNNL-19944).

While considerable progress has been made in developing and applying GIS-based spatiotemporal models of high granularity to siting microalgal growth facilities in terrestrial landscapes in the continental U.S. (Wigmosta et al., 2011), parallel efforts to identify suitable sites for macroalgal cultivation in U.S. marine waters have yet to be reported. Such effort requires development of new analysis tools because those developed for land-based microalgal resources (Wigmosta et al., 2011) are not directly applicable to marine waters. Thus, the plan for subsequent years, starting in FY11, was to develop a multi-year systematic national assessment to evaluate the U.S. potential for macroalgae production using a GISbased assessment tool and biophysical growth model developed as part of these activities. The broad goal of this modeling effort is to develop a National Macroalgae Assessment Model for evaluating macroalgae production in marine waters within the U.S. Exclusive Economic Zone (EEZ). Focus was placed on an assessment of kelp, a group of brown macroalgae considered suitable for conversion to biofuels based on biochemical composition and growth characteristics. Progress in FY11, which focused on model development and initial application of the models to demonstration areas in offshore waters, is described in this report.

During FY11, a concept map describing spatial models to identify suitable sites for producing macroalgae biomass was developed as a framework for conducting a GIS-based national resource assessment within the U.S. EEZ. The spatial models included modeling macroalgae production potential, constrained by competing uses and legal, environmental, and infrastructure considerations at specified locations in the U.S. EEZ. A literature review of these constraints was conducted, and remotely-sensed data sources were identified, downloaded, and processed using 8-day composites from 2000 to 2011 to support site screening and macroalgae growth model development. Model demonstration areas off the Pacific and Atlantic coasts of the United States were identified, and efforts were directed to modeling constraints and production potential within these regions. The overall resource model, conceived as a merged model, consists of a biomass production model (the Macroalgae Growth Model) constrained by conflicting uses of marine waters under U.S. jurisdiction (the Constraints Model). Areas with high constraints are eliminated for further consideration as production sites. This report includes the initial model development and initial application of models to demonstration areas in the U.S. EEZ.

Legal, environmental, and competing use constraints were analyzed and used to construct maps of overall constraints within the demonstration areas. Areas of low, moderate, and high constraints were identified in both of the demonstration areas, with the last identifying locations not advised for macroalgal ii cultivation. The analysis showed that there are fewer conflicts farther from shore. There are also different barriers in different regions. For example, with respect to the demonstration areas, there are greater competing use conflicts in Southern California than in Gulf of Maine. For the physics-based resource assessment, spatiotemporal evaluation of sea surface temperature and photosynthetically-active radiation were used to develop suitability maps for kelp viability for the East and West Coasts of the United States. These showed extensive areas where environmental conditions could sustain populations of macroalgae. Application of a macroalgae growth model developed in this study to the West Coast demonstration area off Southern California showed that warmer water temperatures in the southern portion would impede growth and result in lower overall production of biomass. A plan to merge the results of the constraints and growth models to construct an initial composite assessment has been developed and would be applied in future work, which is contingent on future interest and needs of the Biomass Program. It would include completion of modeling the demonstration areas and expansion to a national assessment that covers the entire U.S. EEZ off the North American continent.

Also conducted were an assessment of infrastructure needs for offshore cultivation based on published and grey literature and an analysis of the type of local, state, and federal requirements that pertain to permitting land-based facilities and nearshore/offshore culture operations. Infrastructure needs include facilities for onshore cultivation and rearing, offshore deployment and rearing, harvesting, and processing. Multiple federal, state, and local laws regulate development and industrial activities on land and in the marine environment. Locating marine aquaculture to offshore sites in the U.S. EEZ would shift the regulatory burden in marine waters to federal agencies. Major information gaps and challenges encountered during this analysis were identified.

Macroalgae, commonly known as seaweed, offer a novel and added-value dietary ingredient in formulated diets for fish. Production of biomass can be achieved without reliance on expensive arable land, as seaweed may be collected from coastal regions or farmed. There are three taxonomic groups represented by the term ‘macroalgae’: Rhodophyta (red), Chlorophyta (green), and Phaeophyta (brown). Like terrestrial plants, nutritional content in macroalgae can vary greatly among species, genera, divisions, seasons and locations. Aside from their basic nutritional value, seaweeds contain a number of pigments, defensive and storage compounds, and secondary metabolites that could have beneficial effects on farmed fish. This review appraises the beneficial qualities of these macroalgae compounds and their potential for exploitation in commercial finfish feeds. The current knowledge of the effects of macroalgae inclusion in finfish diets is also addressed. From these >50 fish feeding studies that were analysed, enhancing trends in fish growth, physiology, stress resistance, immune system, and fillet muscle quality were reported. However, only a small fraction of algal species have so far been investigated as potential components in finfish diets, and furthermore, this review has identified a number of knowledge gaps that current research has yet to address. To conclude, an appraisal is made of the possible technologies employed to exploit seaweeds to an industrial level through stabilising the algal meal, enhancing the digestibility and functional food properties. 

The objective of this project was to demonstrate, at a pilot scale, the beneficial use of carbon dioxide (CO2) through a technology designed to capture CO2 from fossil-fuel fired power plant stack gas, generating macroalgae and converting the macroalgae at high efficiency to renewable methane that can be utilized in the power plant or introduced into a natural gas pipeline.
The proposed pilot plant would demonstrate the cost-effectiveness and CO2/NOx flue-gas removal efficiency of an innovative “algal scrubber” technology where seaweeds are grown out of water on specially-designed supporting structures contained within greenhouses where the plants are constantly bathed by recycled nutrient sprays enriched by flue gas constituents.
The work described in this document addresses Phase 1 of the project only. The scope of work for Phase 1 includes the completion of a preliminary design package; the collection of additional experimental data to support the preliminary and detailed design for a pilot scale utilization of CO2 to cultivate macroalage and to process that algae to produce methane; and a technological and economic analysis to evaluate the potential of the system.
Selection criteria for macroalgae that could survive the elevated temperatures and potential periodic desiccation of near desert project sites were identified. Samples of the selected macroalgae species were obtained and then subjected to anaerobic digestion to determine conversions and potential methane yields. A Process Design Package (PDP) was assembled that included process design, process flow diagram, material balance, instrumentation, and equipment list, sizes, and cost for the Phase 2 pilot plant. Preliminary economic assessments were performed under the various assumptions made, which are purposely conservative. Based on the results, additional development work should be conducted to delineate the areas for improving efficiency, reducing contingencies, and reducing overall costs.