Biodiesel Co-Product (BCP) Decreases Soil Nitrogen (N) Losses to Groundwater

Abstract

This study compares a traditional agricultural approach to minimise N pollution of groundwater (incorporation of crop residues) with applications of small amounts of biodiesel co-product (BCP) to arable soils. Loss of N from soil to the aqueous phase was shown to be greatly reduced in the laboratory, mainly by decreasing concentrations of dissolved nitrate-N. Increases in soil microbial biomass occurred within 4 days of BCP application—indicating rapid adaptation of the soil microbial community. Increases in biomass-N suggest that microbes were partly mechanistic in the immobilisation of N in soil. Straw, meadow-grass and BCP were subsequently incorporated into experimental soil mesocosms of depth equal to plough layer (23 cm), and placed in an exposed netted tunnel to simulate field conditions. Leachate was collected after rainfall between the autumn of 2009 and spring of 2010. Treatment with BCP resulted in less total-N transferred from soil to water over the entire period, with 32.1, 18.9, 13.2 and 4.2 mg N kg−1 soil leached cumulatively from the control, grass, straw and BCP treatments, respectively. More than 99 % of nitrate leaching was prevented using BCP. Accordingly, soils provided with crop residues or BCP showed statistically significant increases in soil N and C compared to the control (no incorporation). Microbial biomass, indicated by soil ATP concentration, was also highest for soils given BCP (p < 0.05). These results indicate that field-scale incorporation of BCP may be an effective method to reduce nitrogen loss from agricultural soils, prevent nitrate pollution of groundwater and augment the soil microbial biomass.

Application of Two Bioenergy Byproducts with Contrasting Carbon Availability to a Prairie Soil: Three-Year Crop Response and Changes in Soil Biological and Chemical Properties

“…In a recent study, glycerol was also found to significantly reduce N loss through minimizing nitrate leaching, owing to microbial immobilization of N [4]. Other bioenergy byproducts with highly available C have also found to cause a short-term immobilization of N [1].…”

“…Similarly, Qian et al [18] reported that N supply from urea fertilizer was adversely affected by glycerol application, especially at the high rates, leading to a significant reduction in plant growth and N uptake. Under growth chamber conditions, glycerol amendment was also shown to immobilize soil available N, as shown by small supply rates of NO 3´-N and NH 4 + -N measured in the soil [20].…”

“…These associated byproducts include biochar (BC), produced during thermal breakdown (pyrolysis) of C-based feedstocks in absence of oxygen [2] and glycerol (GL), generated during the manufacture of biodiesel via transesterification of vegetable oils. Research into finding beneficial means of their utilization is ongoing, including their application to soil [3,4].…”

Zinc toxicity stimulates microbial production of extracellular polymers in a copiotrophic acid soil

“…BCP was selected as a C substrate to support microbial metabolism owing to a global and pressing need to reconcile issues of food security and bioenergy through integrated synergies (Redmile-Gordon et al., 2015b, Kline et al., 2016). The growing range of uses for BCP in soils ranges from the capacity to reduce direct N 2 O emissions (Alotaibi and Schoenau, 2013) preventing NO 3 − contamination of groundwater (Redmile-Gordon et al., 2014a) and supporting production of EPS via the native soil microbial biomass (Redmile-Gordon et al., 2015b). …”

Engineering soil organic matter quality: Biodiesel Co-Product (BCP) stimulates exudation of nitrogenous microbial biopolymers

“…More direct uses of BCP offer intriguing environmental prospects, e.g., as a component of soil treatments to engineer improved (or repair lost) soil functions. The application of BCP to soil as a substrate for the native soil microbial biomass was previously found to be > 99% effective in causing nitrate (NO 3 ) capture from soil solution and thus preventing loss from surface horizon (23 cm) in winter ( Redmile-Gordon et al, 2014a ). BCP therefore has considerable potential for improving nitrogen use-efficiency and limiting the environmental damage caused by ‘leaky’ agriculture.…”