Reviewer Comments - EERE

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2011 Algae Platform Review – Reviewer Comments Reviewer Comments are direct transcripts of commentary and material provided by the Platform’s Review Panel. They have not been edited or altered by the Biomass Program. Reviewer: 3 Anaerobic Digestion : What are the anaerobic microbes involved? Please define them for the benefit of the review process. Is there progress so far in AD? The reviewer's recommendation for the PSI is to seek protein degradation (proteases) and cell wall degradation (cellulases) by which to pre-digest the biomass. Breaking up the biomass into the constituent components would substantially improve yields. Reviewer: 4 Overall Impression: 6 The research goals are important and relevant, but the digestion results of future systems will depend on which algae are grown, the growth conditions, and the particular oil extraction method (current solvent extractions of all types have cost and other barriers). This project tries to cover the first two points by studying several species and growing them under conditions that might be used at full-scale. These are still somewhat speculative, but the oil recovery methods of the future are an even greater unknown. Thus, this project will be able to provide methane yield and production estimates for some speculative future conditions. However, even these preliminary results will be valuable. Presumably, the biochemical composition of the digester influent (and effluent) will be quantified and controlled, although this is not mentioned in the presentation. The emphasis on growing algae specifically for this project may consume most of the project effort. Only marginally sufficient biomass quantities might be produced using the small-scale culturing equipment implied by the presentation. Efforts should be made to identify another research group that is producing larger quantities of algae and extracting it and would be willing to share the residuals. The 2 kg from Seambiotic is a good start. Small, presumably batch, digestion experiments are planned for 12 months, prior to setup of 1-L, presumably semi-continuous-feed, digesters. Operation of only batch digesters for 12 months seems excessive because the more realistic data will come from the 1-L semi-continuous digesters, which appear to be scheduled to operate for only 4 months--a marginal amount of time to collect steady state data. The planned loading rate and C:N studies should not be the main emphasis because they are likely to give results similar to digestion of conventional wastes. Algae biochemical composition and oil extraction procedures are likely to be the dominant variables with respect to methane yield. The primary experiments should explore a range of these two variables. The algae regrowth work is valuable if light attenuation by the digester effluent is considered as one of the variables. What makes you think that the enzyme treatment will be affordable? Reviewer: 5 The use of algal biomass from laboratory grown cultures drastically reduces the relevance of this project. Given the extensive knowledge base about anaerobic digestion, the funding level, and the two year project period, the goals appeared very modest. Reviewer: 6 No real justification for any of the steps taken. Page 148 of 223
2011 Algae Platform Review – Reviewer Comments Reviewer Comments are direct transcripts of commentary and material provided by the Platform’s Review Panel. They have not been edited or altered by the Biomass Program. Reviewer: 7 The project could benefit from specific quantitative goals based on commercial requirements for the process and the economics. The extent of the technology survey that has been completed by the team is not clear. Presenter Response Many of these comments are addressed above. Regarding the emphasis on batch digesters vs. larger scale semi-continuous digesters, that is a useful comment and we will do as much work at the larger scale as time and materials allow. However, our work at the smaller scale will provide much higher throughput and therefore the testing of many more variables. We believe that this approach will allow for better optimized digestions and maximize the output of useful data. The cost of enzymatic treatments, if they are shown to be effective, will be modeled. Recent advances in the production of low-cost enzymes for lignocellulosic ethanol processes suggest that such options may be affordable. We apologize if the presentation did not adequately convey the justification for this work. As noted above, when considering a process that currently is predicted to reduce algal lipid costs by $2.22 per gallon, it is important that the underlying assumptions be tested. Co-products are essential to an economically viable process, and any potential producer weighing the various options will want to make decisions based on actual data rather than assumptions. As discussed above, the possible need for co-feedstock will be an important outcome. We plan to use relatively defined co-feedstocks for initial studies (primarily cellulose), but may be able to test alternative low-cost materials. Regarding a question about recylcing of the AD sludge, we believe that sludge recycle may be problematic. Current scenarios focus on the liquid fraction of the effluent. Regarding a suggestion that algal residues simply be burned for power generation, anaerobic digestion for biogas/biopower has several advantages over a simple combustion scenario. In particular, the drying step required before combustion adds very significant costs and energy consumption to the process. Also, nutrient recycle would be more difficult; combustion of this high-protein feedstock would likely release much of the nitrogen as NOx, making recycle difficult and resulting in air pollution issues. Specific quantitative goals are discussed above under Project Approach. Project: 9.1.2.2 Sandia National Laboratories Title: Pond Crash Forensics Presenter: Todd Lane Presentation Date: Friday, April 08, 2011 Criteria Avg Score Std Deviation Count Approach 6.00 1.41 7 Progress 5.86 1.36 7 Relevance 6.00 1.93 7 Critical Success Factors 5.43 1.59 7 1. Project Approach The project performers have implemented technically sound research, development, and deployment approaches and demonstrated necessary results to meet their targets The project performers have identified a project management plan that includes well-defined milestones and adequate methods for addressing potential risks. Page 149 of 223
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Reviewer Comments - EERE

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