Optimal integrated facility for waste processing

Analysis of incentive policies for phosphorus recovery at livestock facilities in the Great Lakes area

Livestock operations have been highly intensified over the last decades, resulting in the advent of large concentrated animal feeding operations (CAFOs). Intensification decreases production costs but also leads to substantial environmental impacts. Specifically, nutrient runoff from livestock waste results in eutrophication, harmful algal blooms, and hypoxia. The implementation of nutrient recovery systems in CAFOs can abate nutrient releases and negative ecosystem responses, although they might negatively affect the economic performance of CAFOs. We design and analyze potential incentive policies for the deployment of phosphorus recovery technologies at CAFOs considering the geospatial vulnerability to nutrient pollution. The case study demonstration consists of 2217 CAFOs in the U.S. Great Lakes area. The results reveal that phosphorus recovery is more economically viable in the largest CAFOs due to economies of scale, although they also represent the largest eutrophication threats. For small and medium-scale CAFOs, phosphorus credits progressively improve the profitability of nutrient management systems. The integration of biogas production does not improve the economic performance of phosphorus recovery systems at most of CAFOs, as they lack enough size to be cost-effective. Phosphorus recovery proves to be economically beneficial by comparing the net costs of nutrient management systems with the negative economic impact derived from phosphorus releases. The incentives necessary for avoiding up to 20.7×10³ ton/year phosphorus releases and achieve economic neutrality in the Great Lakes area are estimated at $223 million/year. Additionally, the fair distribution of limited incentives is studied using a Nash allocation scheme, determining the break-even point for allocating monetary resources.

A geospatial environmental and techno-economic framework for sustainable phosphorus management at livestock facilities

Nutrient pollution of waterbodies is a major worldwide water quality problem. Excessive use and discharge of nutrients can lead to eutrophication and algal blooms in fresh and marine waters, resulting in environmental problems associated with hypoxia, public health issues related to the release of toxins and freshwater scarcity. A promising option to address this problem is the recovery of nutrient releases prior to being discharged into the environment. Driven by the sustainable materials management concept, the COW2NUTRIENT (Cattle Organic Waste to NUTRIent and ENergy Technologies) framework is developed for the techno-economic evaluation and selection of nutrient recovery systems at livestock facilities. Environmental vulnerability to nutrient pollution determined through a geographic information system (GIS)-based model and techno-economic information of different state-of-the-art nutrient management technologies are combined in a multi-criteria decision analysis (MCDA) model, resulting in the selection and economic analysis of the most suitable process for each studied livestock facility. This framework has been employed for studying the implementation of sustainable phosphorus management systems at 2,217 livestock facilities in the Great Lakes area, resulting in capital expenses of 2.5 billion USD if only phosphorus recovery technologies are installed, and up to 5.2 billion USD if nutrient management is combined with biogas and power production. However, considering potential economic incentives for the recovery of phosphorus, net revenues up to 230 million USD per year can be achieved. Therefore, the framework presented reveals the potential of implementing nutrient management systems at regional scale for the abatement of phosphorus releases from livestock facilities.

Growing phosphorus dilemma: The opportunity from aquatic systems' secondary phosphorus retention capacity

The essential cause of phosphorus scarcity and phosphorus-induced risks, i.e. phosphorus dilemma, mainly lies in current low phosphorus flow efficiency (PFE) in agricultural systems. Improving PFE largely depends on secondary phosphorus retention along the phosphorus flow chain from phosphate mining to terrestrial agricultural systems, to aquatic systems, and ultimately to seabed deposition. Our review found that aquatic systems will have the opportunity and growing capacity to retain seaward secondary phosphorus carried by the runoff, due to its location between land and water systems, its ability of converting secondary phosphorus from both land and aquatic systems into aquatic products, and its rapid expansion with low PFE. However, a knowledge gap exists in secondary phosphorus retention in aquatic systems compared to in terrestrial systems. Although the phosphorus retention literature continues to grow in environmental and agricultural & biological sciences, only 8.8% of the documents are related to aquatic systems with few quantification studies. Based on the literature with phosphorus retention quantification since 1979, we divided the reported phosphorus interceptors into abiotic and biotic groups, further into 7 categories and more subcategories. By 2020, eight categories of interceptors had been reported, increased from only one interceptor in 1979. However, most of them focused on wetlands, only a few studies on aquatic organisms which concentrated in 8 countries before 2000. Thus, it is urgent to emphasize aquatic systems' secondary phosphorus retention capacity and its systemic benefits for a sustainable phosphorus use.

Life Cycle Assessment of Struvite Precipitation from Anaerobically Digested Dairy Manure: A Wisconsin Perspective

Recovering valuable nutrients (e.g., P and N) from waste materials has been extensively investigated at the laboratory scale. Although it has been shown that struvite precipitation from several manure sources contributes to nutrient management practices by recovering valuable nutrients and preventing them from reaching water bodies, it has not been widely applied in commercial (i.e., farm) scales. The purpose of this study is to evaluate the potential environmental impacts of the struvite recovery process from the liquid portion of the anaerobically digested dairy cow manure generated in Wisconsin, USA, dairy farms using life cycle assessment methodology for both bench- and farm-scale scenarios. The struvite precipitation process involves the use of additional chemicals and energy; therefore, investigating upstream impacts is crucial to evaluate the environmental costs and benefits of this additional treatment process. Results indicate that up to a 78% impact decrease in eutrophication potential can be achieved when P and N are recovered in the form of struvite and are applied in lieu of conventional fertilizers, rather than using the liquid portion of the anaerobically digested dairy manure as a fertilizer. Additionally, significant differences are identified in the majority of environmental impact categories when the struvite precipitation process is modeled and evaluated in a farm-scale setting. Future work should expand to evaluate the overall environmental impacts and trade-offs of struvite recovery application, including the anaerobic digestion system itself at the farm scale. Integr Environ Assess Manag 2021;17:292-304. © 2020 SETAC.

Model-driven spatial evaluation of nutrient recovery from livestock leachate for struvite production

Nutrient pollution is one of the major worldwide water quality problems, resulting in environmental and public health issues. Agricultural activities are the main source of nutrient release emissions, and the livestock industry has been proven to be directly related to the presence of high concentrations of phosphorus in the soil, which potentially can reach waterbodies by runoff. To mitigate the phosphorus pollution of aquatic systems, the implementation of nutrient recovery processes allows the capture of phosphorus, preventing its release into the environment. Particularly, the use of struvite precipitation produces a phosphorus-based mineral that is easy to transport, enabling redistribution of phosphorus to deficient locations. However, livestock leachate presents some characteristics that hinder struvite precipitation, preventing extrapolation of the results obtained from wastewater studies to cattle waste. Consideration of these elements is essential to determine the optimal operating conditions for struvite formation, and for predicting the amount of struvite recovered. In this work, a detailed thermodynamic model for precipitates formation from cattle waste is used to develop surrogate models to predict the formation of struvite and calcium precipitates from cattle waste. The variability in the organic waste composition, and how it affects the production of struvite, is captured through a probability framework based on the Monte Carlo method embedded in the model. Consistent with the developed surrogate models, the potential of struvite production to reduce the phosphorus releases from the cattle industry to watersheds in the United States has been assessed. Also, the more vulnerable locations to nutrient pollution were determined using the techno-ecological synergy sustainability metric (TES) by evaluating the spatial distribution and balance of phosphorus from agricultural activities. Although only struvite formation from cattle operations is considered, reductions between 22% and 36% of the total phosphorus releases from the agricultural sector, including manure releases and fertilizer application, can be achieved.

Effective Use of Carbon Pricing on Climate Change Mitigation Projects: Analysis of the Biogas Supply Chain to Substitute Liquefied-Petroleum Gas in Mexico

There is presently an urgent demand for efficient and/or renewable energy technologies to correct global warming. However, these energy technologies are limited mainly by political and economic constraints of high costs and the lack of subsidy. Carbon-pricing strategies, such as carbon-emission taxes and carbon-emission trading schemes, may reduce this gap between sustainable and unsustainable energy technologies. Therefore, this paper seeks to analyze both of these carbon-pricing instruments in the Mexican energy sector to promote upgrading biogas investment and to substitute liquified petroleum gas consumption using an optimization approach. Furthermore, we propose a multi-objective optimization approach to encourage investment in the biogas supply chain supported by an effective use of carbon-pricing schemes. A case study of the central western region of Mexico was made to analyze the performance of the proposed methodologies. The results show that carbon-emission taxes and carbon-emission trading systems stimulate, with some limitations, the investment in biogas projects for fossil fuel substitution. Nevertheless, using the proposed multi-objective optimization formulation leads the discovery of a more efficient use of the above-mentioned carbon-pricing schemes, thus reaching higher economic and environmental benefits than traditional carbon-pricing policies, with a lower cost/price per ton of carbon dioxide equivalent.

Economic and Environmental Analysis for Advancing Sustainable Management of Livestock Waste: A Wisconsin Case Study

Livestock waste may cause some air quality degradation from ammonia and methane emissions, soil quality detriment due to in-excess nutrients and acidification, and water pollution issues resulting from nutrient and pathogens runoff to water bodies, which leads to eutrophication, algal blooms, and hypoxia. Despite the significant environmental benefits by performing pollution management of these organic materials, the recovery of value-added products from livestock waste is not a current practice due to the high investment costs required and to the low market values being offered for the products that are recovered. Therefore, we present a supply chain design framework to conduct simultaneous economic and environmental analysis of post-livestock organic material to value-added products. The proposed framework captures techno-economic and logistical issues and can accommodate diverse types of policy incentives obtained at federal and state levels, allowing stakeholders to conduct systematic studies on the effect of incentives on economic and environmental viability of different technologies. We apply the framework to a case study for dairy farms in the State of Wisconsin (U.S.). The framework reveals that, from a purely economic perspective, products recovered from dairy waste are not competitive at current market prices. We also find that incorporating current and potential U.S. government incentives in the form of Renewable Identification Numbers (RINs) and phosphorus credits can achieve economic viability of the recovery of liquefied biomethane and nutrient-rich products. On the other hand, current incentives for electricity generation (Renewable Energy Credits or RECs) would not achieve economic viability. The analysis also reveals that the best strategy to manage waste is to synergize the deployment of technologies that conduct simultaneous recovery of liquefied biomethane and nutrients.