This techno-economic analysis/life-cycle assessment is based on actual production by the Cornell Marine Algal Biofuels Consortium with biomass productivity > 23 g/m 2-d. Ten distinct cases are presented for two locations, Texas and Hawaii, based on a 100-ha production facility with end-to-end processing that yields fungible co-products including biocrude, animal feed, and ethanol. Several processing technologies were evaluated: centrifugation and solvent extraction (POS Biosciences), thermochemical conversion (Valicor), hydrothermal liquefaction (PNNL), catalytic hydrothermal gasification (Genifuel), combined heat and power, wet extraction (OpenAlgae), and fermentation. The facility design was optimized by co-location with waste CO 2 , a terraced design for gravity flow, using renewable energy, and low cost materials. The case studies are used to determine the impact of design choices on the energy return on investment, minimum fuel and feed sale prices, discounted payback period, as well as water depletion potential, human health, ecosystem quality, non-renewable resources, and climate change environmental indicators. The most promising cases would be economically competitive at market prices around $2/L for crude oil, while also providing major environmental benefits and freshwater savings. As global demands for fuels and protein continue rising, these results are important steps towards economical and environmentally sustainable production at an industrial scale.

As a result of algae's promise as a renewable energy feedstock, numerous studies have used Life Cycle Assessment (LCA) to quantify the environmental performance of algal biofuels, yet there is no consensus of results among them. Our work, motivated by the lack of comprehensive uncertainty analysis in previous studies, uses a Monte Carlo approach to estimate ranges of expected values of LCA metrics by incorporating parameter variability with empirically specified distribution functions. Results show that large uncertainties exist at virtually all steps of the biofuel production process. Although our findings agree with a number of earlier studies on matters such as the need for wet lipid extraction, nutrients recovered from waste streams, and high energy coproducts, the ranges of reported LCA metrics show that uncertainty analysis is crucial for developing technologies, such as algal biofuels. In addition, the ranges of energy return on (energy) invested (EROI) values resulting from our analysis help explain the high variability in EROI values from earlier studies. Reporting results from LCA models as ranges, and not single values, will more reliably inform industry and policy makers on expected energetic and environmental performance of biofuels produced from microalgae.

Fourier transform infrared, attenuated total reflectance (FTIR-ATR) spectroscopy combined with partial least squares (PLS) regression accurately predicted 72-h glucose and xylose conversions (g sugars/100 g potential sugars) and yields (g sugars/100 g dry solids) from cellulase-mediated hydrolysis of alkali-pretreated lignocellulose. Six plant biomasses that represent a variety of potential biofuel feedstocks--two switchgrass cultivars, big bluestem grass, a low-impact, high-diversity mixture of 32 species of prairie biomasses, mixed hardwood, and corn stover--were subjected to four levels of low-temperature NaOH pretreatment to produce 24 samples with a wide range of potential digestibility. PLS models were constructed by correlating FTIR spectra of pretreated samples to measured values of gluose and xylose conversions and yields. Variable selection, based on 90% confidence intervals of regression-coefficient matrices, improved the predictive ability of the models, while simplifying them considerably. Final models predicted sugar conversions with coefficient of determination for cross-validation (Q(2)) values of 0.90 for glucose and 0.89 for xylose, and sugar yields with Q(2) values of 0.92 for glucose and 0.91 for xylose. The sugar-yield models are noteworthy for their ability to predict enzymatic saccharification per mass dry solids without a priori knowledge of the composition of the solids. All peaks retained in the final regression coefficient matrices were previously assigned to chemical bonds and functional groups in lignocellulose, demonstrating that the models were based on real chemical information. This study demonstrates that FTIR spectroscopy combined with PLS regression can be used to rapidly estimate sugar conversions and yields from enzymatic hydrolysis of pretreated plant biomass.

We present the results from sustained tonne-quantity production of two novel strains of marine microalgae, the diatom Staurosira and the chlorophyte Desmodesmus, cultivated in a hybrid system of 25-m 3 photobioreactors and 400-m 2 open ponds at a large-scale demonstration facility, and then apply those results to evaluate the performance of a 100-ha Base Case commercial facility assuming it were built today. Nitrogen fertilization of 2-d batch cultures in open ponds led to the greatest yields-from both species-of ~75 MT ha-1 yr-1 biomass, and ~30 MT ha-1 yr-1 lipid, which are unprecedented in large scale open pond systems. The process described here uses only seawater, discharges no nitrogen or phosphorus in any form, and consumes CO 2 at 78% efficiency. We estimate the capital cost of a 111-ha Base Case facility at $67 million in Hawaii, where actual production was performed, and $59 million on the Gulf Coast of Texas. We find that large-diameter, large-volume PBRs are an economical means to maintain a continuous supply of consistent inoculum for very short-period batch cultures in open ponds, and thus avoid biological system crashes that otherwise arise in longer-term pond cultures. We recommend certain improvements in cultivation methods that could realistically lead to yields of 100 MT ha-1 yr-1 biomass and >50,000 L ha-1 yr-1 algal oil. Comprehensive techno-economics and life cycle assessment of 20 endto-end production lineups, based on the cultivation results in this paper, are presented in a companion paper by Beal et al [1].

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The objective of this study was to elucidate the effect of adding acid and alkali to hydrothermal liquefaction (HTL) of two waste biomass feedstocks: manure digestate and carbohydrate-rich food waste. HTL reactions were conducted at 300 °C for 60 min, with and without the addition of acid or base. We measured the quantity and characterized the quality of the three main HTL products: oil, aqueous and hydro-char. For both feedstocks, carbon recovery distributions had wide ranges among (1) biocrude oil (26–61 wt %), (2) aqueous product (9–49 wt %) and (3) hydro-char (1–36 wt %). The addition of acid affected HTL reactions for manure more than for food waste. For the aqueous phase, the addition of acid decreased the recovery of C1–4 carboxylic acids and increased the production of cyclic furan compounds. GC–MS analysis of the biocrude oil suggested that dehydration reactions were enhanced by adding acid to the HTL media. FTIR spectroscopy coupled with principal component analysis showed that hydro-char samples cluster according to acid-modified and base-modified reactions, based on distinct chemical structures. This study clarifies the role of pH during HTL and its effect on chemical pathways and carbon distribution among products.

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Production of economically competitive and environmentally sustainable algal biofuel faces technical challenges that are subject to high uncertainties. Here we identify target values for algal productivity and financing conditions required to achieve a biocrude selling price of $5 per gallon and beneficial environmental impacts. A modeling framework--combining process design, techno-economic analysis, life cycle assessment, and uncertainty analysis--was applied to two conversion pathways: (1) "fuel only (HTL)", using hydrothermal liquefaction to produce biocrude, heat and power, and (2) "fuel and feed", using wet extraction to produce biocrude and lipid-extracted algae, which can substitute components of animal and aqua feeds. Our results suggest that with supporting policy incentives, the "fuel and feed" scenario will likely achieve a biocrude selling price of less than $5 per gallon at a productivity of 39 g/m(2)/day, versus 47 g/m(2)/day for the "fuel only (HTL)" scenario. Furthermore, if lipid-extracted algae are used to substitute fishmeal, the process has a 50% probability of reaching $5 per gallon with a base case productivity of 23 g/m(2)/day. Scenarios with improved economics were associated with beneficial environmental impacts for climate change, ecosystem quality, and resource depletion, but not for human health.