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Due to mounting impacts of climate change, particularly increased incidence of drought, hence water scarcity, it has become imperative to develop new technologies for recovering water from nutrient-rich, water-replete effluents other than sewage. Notably, anaerobic digestate could be harnessed for the purpose of water recovery by repurposing digestate-borne minerals as nutrients in fermentative processes. The high concentrations of ammonium, phosphate, sulfate, and metals in anaerobic digestate are veritable microbial nutrients that could be harnessed for bio-production of bulk and specialty chemicals. Tethering nutrient sequestration from anaerobic digestate to bio-product accumulation offers promise for concomitant water recovery, bio-chemical production, and possible phosphate recovery. In this review, we explore the potential of anaerobic digestate as a nutrient source and as a buffering agent in fermentative production of glutamine, glutamate, fumarate, lactate, and succinate. Additionally, we discuss the potential of synthetic biology as a tool for enhancing nutrient removal from anaerobic digestate and for expanding the range of products derivable from digestate-based fermentations. Strategies that harness the nutrients in anaerobic digestate with bio-product accumulation and water recovery could have far-reaching implications on sustainable management of nutrient-rich manure, tannery, and fish processing effluents that also contain high amounts of water. Key points: • Anaerobic digestate may serve as a source of nutrients in fermentation. • Use of digestate in fermentation would lead to the recovery of valuable water. [ABSTRACT FROM AUTHOR]

Aquaponics is often presented as a sustainable food production system that can reduce environmental costs of global food production; yet, its actual environmental effects are understudied. The aim of this research was to review the limited number of life cycle assessment studies dealing with aquaponics, and to highlight environmental cost and benefit of this practice. Our assessment highlights some of the problems, challenges, and advantages of aquaponics as a valuable food production system. We propose guidelines for future life cycle assessments of aquaponics that will facilitate policy and decision-making for farmers with respect to aquaponics. [ABSTRACT FROM AUTHOR]

Biofuels vary greatly in their carbon intensity, depending on the specifics of how they are produced. Policy frameworks are needed to ensure that biofuels actually achieve intended reductions in greenhouse gas emissions. Current approaches do not account for important variables during cultivation that influence emissions. Estimating emissions based on biogeochemical models would allow accounting of farm-specific conditions, which in turn provides an incentive for producers to adopt low emissions practices. However, there are substantial uncertainties in the application of biogeochemical models. This paper proposes a policy framework that manages this uncertainty while retaining the ability of the models to account for (and hence incentivize) low emissions practices. The proposed framework is demonstrated on nitrous oxide (N2O) emissions from the cultivation of winter barley. The framework aggregates uncertainties over time, which (1) avoids penalizing producers for uncertainty in weather, (2) allows for a high degree of confidence in the emissions reductions achieved, and (3) attenuates the uncertainty penalties borne by producers within a timescale of several years. Results indicate that with effective management, N2O emissions from feedstock cultivation may be < 5% of the carbon intensity of gasoline, whereas the existing policy approach estimates emissions > 20% of the carbon intensity of gasoline. If these emissions reductions are monetized, the framework can provide up to $0.002 per liter credits (0.8 cents per gallon) to fuel producers, which could incentivize emissions mitigation practices by biofuel feedstock suppliers, such as avoiding fall N application on silty clay loam soils. The conservatism in the current approach fails to incentivize the adoption of biofuels, while the lack of specificity fails to incentivize site-level mitigation practices. Improved uncertainty accounting and consideration of farm-level practices will incentivize mitigation efforts at landscape to global scales. [ABSTRACT FROM AUTHOR]

A life cycle assessment (LCA) and cost analysis were conducted to compare the environmental and economic performance of nanocomposite polymers that use pristine and recycled high density polyethylene (HDPE) polymer with pristine, and pristine/recycled HDPE polymeric materials in drainage pipe. We evaluate three performance metrics; (a) non-renewable energy consumption (NRE); (b) greenhouse gas (GHG) emissions; and (c) production costs of the three pipe material alternatives. Original life cycle inventory data for the production of nanoclay from the mineral Montmorillonite were collected for this case study in the United States. Life cycle inventory models were developed for the cradle-to-gate production of drainage pipe used in highway construction that consider the sensitivity of model parameter inputs on the life cycle impact and cost results for the three material options. The GHG emissions for the nanoclay composite pipe are 54 % lower than those for pristine HDPE pipe, and 16 % lower than those for pristine/recycle HDPE pipe. With a slight difference in GHG emissions between the pristine/recycled and nanoclay composite, the production of nanoclay does not introduce a significant environmental burden to the pipe material. On average, the pristine HDPE pipe is 13 and 17 % higher in cost than the pristine/recycled HDPE and nanoclay composite pipes, respectively. Results of the LCA and cost analysis support using recycled HDPE as a substitute for pristine HDPE due to its low energy requirements and production costs. The uncertainty in GHG emissions of manufacturing pristine HDPE causes the largest variation of GHG emissions in nanoclay composite pipe (+3/−2 %). The production cost of the nanocomposite pipe is most influenced by the energy cost of PCR-HDPE (+25/−11 %). Our study suggests that a nanocomposite design that replaces part of the pristine HDPE with recycled HDPE and nanoclay reduces certain environmental risks and material cost of corrugated pipe. [ABSTRACT FROM AUTHOR]

The growing availability of software tools has increased the speed of generating LCA studies. Databases and visual tools for constructing material balance modules greatly facilitate the process of analyzing the environmental aspects of product systems over their life cycle. A robust software tool, containing a large LCI dataset and functions for performing LCIA and sensitivity analysis will allow companies and LCA practitioners to conduct systems analyses efficiently and reliably. This paper discusses how the GaBi 3 software tool can be used to perform LCA and Life Cycle Engineering (LCE), a methodology that combines life cycle economic, environmental, and technology assessment. The paper highlights important attributes of LCA software tools, including high quality, well-documented data, transparency in modeling, and data analysis functionality. An example of a regional power grid mix model is used to illustrate the versatility of GaBi 3. [ABSTRACT FROM AUTHOR]

Life Cycle Assessment is becoming an important tool for guiding environmental design improvements in the automotive industry. This paper reports the life cycle inventory profiles for two fuel tank systems based on a collaborative effort between the National Pollution Prevention Center at the University of Michigan, General Motors Research and Development, and the National Risk Management Research Laboratory of the U.S. Environmental Protection Agency. Two 31 gallon functionally equivalent fuel tank systems used on a 1996 light duty vehicle were investigated: a multi-layer HDPE tank with a steel shield and PVC coated steel straps, and a steel tank with a HDPE shield and painted steel straps. Overall, the HDPE fuel tank system is environmentally preferable to the steel tank system based on the set of inventory results presented in this investigation. The Life Cycle Inventory analysis indicated lower energy burdens for the HDPE tank system and comparable solid waste burdens for both systems. The total life cycle energy consumption for the steel and HDPE tank systems were 4.9 GJ and 3.6 GJ per tank, respectively. The energy consumption and most of the air pollutants inventoried occurred as a consequence of the use phase. The solid wastes were generated primatily during the material production phase for the steel tank (13 kg) and during the end-of-life management phase for the HDPE tank (14 kg). This study also highlights data analysis and modeling challenges, including manufacturing and use phase allocation methods. [ABSTRACT FROM AUTHOR]