Question 3: Are microalgae a viable means of improving soil quality on reclaimed mine land?

Due to extensive mining in both the eastern part of the state, Kentucky is among the states with the greatest proportion of mine lands in need of reclamation. Mine soil is generally of poor quality for vegetation, and reclamation efforts aimed at enhancing soil quality typically focus on physical, chemical, and biological soil parameters, including soil organic matter (SOM), organic and mineralizable carbon and nitrogen, microbial community structure and function, water holding capacity, aeration, aggregate stability, nutrient availability, pH, and bulk density [1]. These parameters are directly linked to plant productivity on reclaimed mine sites. Against this background, the application of biofertilizers in more conventional soils has been shown to positively impact crop yield and soil quality parameters (such as SOM and organic nitrogen) and decrease greenhouse gas (GHG) emissions [2]. Further, biofertilizers have been shown to have positive effects on crops grown under toxic metal stress, including growth enhancement and stress amelioration [3]. While biofertilizers can include many different types of biological materials (e.g., bacteria, fungi, etc.), the studies above used algae [2,3], which offer several benefits, as they generate biomass through photosynthesis and accumulate compounds that may be beneficial when applied as fertilizer, including lipids, proteins, carbohydrates, phytohormones, and amino acids [4]. Furthermore, increasing organic matter in soils may result in greenhouse gas benefits, such as improved workability of soils, better water retention, decreased use of mineral fertilizers and pesticides, and reduced release of N2O [5].

The use of algae as a biofertilizer is particularly appealing for several other reasons. First, biofertilizer derived from algae grown using CO2 emissions benefits the environment since the carbon is effectively recycled. Appalachia has many industrial CO2 point sources, mainly in the form of power plants. Notably, in work funded by the Department of Energy, UK researchers have been actively evaluating the potential of microalgae for CO2 bio-mitigation at power plants since 2012 [6-10] and have licensed its algae cultivation technology to a commercial partner (Lianhenghui Investment Co.) in China [11]. Moreover, the N, P, and K required for algae cultivation can be provided by wastewater streams, if these are available. Currently, academic studies characterizing the use of microalgae as a biofertilizer are largely lacking, although at least one company is commercializing an algae-based soil additive [12], and several reports suggest that microalgae could represent a promising alternative to commercial organic fertilizers [13,14].

Drawing on these studies and the project team’s extensive knowledge of algae cultivation, we will develop a TEA and LCA for the utilization of algae biofertilizer to enhance reclaimed mine land soil quality. Specifically, the TEA will utilize a simulation approach to evaluate the use of algae biofertilizers relative to conventional fertilizers. Through this study, data will be collected for the cost of production, nutrient availability (e.g., N, P, and K), application costs, and transportation costs for algae biofertilizers. Secondly, a LCA will be developed for the application of algae biofertilizers. Data collected on expected crop yields, nutrient value, transportation distance and method will be key factors. Thus, we propose to examine the agronomic and economic feasibility of algae for improving the soil quality in flat and accessible reclaimed mine land areas to facilitate their use for agricultural production.

Specific questions to be addressed in this work will include the following: how does microalgal biomass impact plant biomass compared to conventional fertilization? Does this differ according to plant species? Which crops are most likely to receive benefits? Does microalgal biomass inoculation decrease the uptake of heavy metals? How does microalgal biomass affect the physical/chemical parameters of reclaimed soil (including SOM, water holding capacity, mineralizable C/N and C/N ratios, and pH)? How does microalgal biomass affect soil microbial community structure and function?  What about the impact to ecosystem services in general (e.g., runoff, leaching, GHG emissions)? What are the economic and lifecycle implications of biofertilizers compared to conventional fertilizers?

This work requires extensive interdisciplinary collaboration between plant and soil science, chemistry, biology, and economics, thus providing a rich ground for graduate student training.




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