Ecological Engineering for Optimal Management of Agricultural and Municipal Organic Residues

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Clark’s Ecological Engineering Research Group has performed innovative research on the creation and management of ecosystems that provide services or solutions. The group uses computational modeling and physical experimentation in parallel. Their recent work on in-vessel composting has led to industry and municipal research partnerships on compost production and utilization. Related work investigated models of large-scale nutrient cycling and on the feasibility of Integrated Assessment Modeling of regional agricultural systems.The group is now strongly positioned to study the flow of nutrients through human-dominated ecosystems. In industrialized economies, the principle crop nutrients are unsustainably sourced. Nitrogen fertilizer is fixed from the atmosphere at a huge energy cost and phosphorous and potassium fertilizers are extracted from nonrenewable mineral deposits. These nutrients are applied to agricultural land, concentrated in cities as part of the food supply chain, and then dispersed in the environment. The challenges are increasing, as growing population and affluence will double demand for food by midcentury. At the same time, rising energy costs and depletion of mineral resources will make fertilizers more expensive. These nutrients are increasingly concentrated in growing cities as urbanization continues worldwide. Long-term sustainability of food and biomass production demands that nutrients be recycled back to production, by the disruptive, large-scale reinvention of waste management systems.In the short term, the group’s prior experience strongly positions them to advance: (1) computational modeling of multi-scale material and energy flows, and (2) the recycling of organic residues. The first research thrust will focus on multi-scale simulation of material and energy flows. The work will expand on the concept of urban metabolism, characterizing nutrient transport from agricultural land, to cities, and into the environment. Strategies will then be evaluated for disruptive change in waste management systems, to instead recycle nutrients back to agricultural production. Technologies such as large-scale composting of organic residuals could direct reclaimed nutrients back to traditional agricultural land or to urban agriculture initiatives. This work will be conducted at the doctoral and research associate level, through strong interdisciplinary collaboration with Clark’s government, industry, and academic colleagues.The second research thrust is the physical and computational modeling of compost production to recycle organic residues. This work is necessary to evaluate technologies proposed as part of the large-scale systems models. Preliminary work by Clark’s group shows promise in adding biochar to compost to reduce gas emissions and retain nitrogen. New work will optimize the degradation in compost of novel biopolymers. Replicated physical experiments will be run in existing pilo-scale composting vessels, instrumented for automated measurement of temperature and gas emissions. This work will be the primary focus of the MSc stream of the lab group.These combined efforts will elevate the group’s combined expertise to make even greater contributions to the development of a sustainable economy based on the rational management of the planet’s finite biological resources. On a large horizon, the work will inform regional and national policy for the sustainable production of food and biomass. The work will contribute in the mid-term to the development of standards and protocols for organics recycling, as many municipalities scramble to implement recycling and composting programs. At a smaller scale, innovation in composting technology and utilization will benefit the group’s industrial and municipal partners.