Advanced Processing of Food Waste Based Digestate for Mitigating Nitrogen Losses in a Winter Wheat Crop

Abstract

The anaerobic digestion of food waste converts waste products into "green" energy. Additionally, the secondary product from this process is a nutrient-rich digestate, which could provide a viable alternative to synthetically-produced fertilizers. However, like fertilizers, digestate applied to agricultural land can be susceptible to both ammonia (NH 3 ) and nitrous oxide (N 2 O) losses, having negative environmental impacts, and reducing the amount of N available for crop uptake. Our main aim was to assess potential methods for mitigating N losses from digestate applied to a winter wheat crop and subsequent impact on yield. Plot experiments were conducted at two UK sites, England (North Wyke-NW) and Wales (Henfaes-HF), to assess NH 3 and N 2 O losses, yield and N offtake following a single band-spread digestate application. Treatments examined were digestate (D), acidified-digestate (AD), digestate with the nitrification inhibitor DMPP (D+NI), AD with DMPP (AD+NI), and a zero-N control (C). Ammonium nitrate (NH 4 NO 3 ) fertilizer N response plots (from 75 to 300 kg N ha −1 ) were included to compare yields with the organic N source. Across both sites, cumulative NH 3 -N losses were 27.6% from D and D+NI plots and 1.5% for AD and AD+NI of the total N applied, a significant reduction of 95% with acidification. Cumulative N 2 O losses varied between 0.13 and 0.35% of the total N applied and were reduced by 50% with the use of DMPP although the differences were not significant. Grain yields for the digestate treatments were 7.52-9.21 and 7.23-9.23 t DM ha −1 at HF and NW, respectively. Yields were greater from the plots receiving acidified-digestate relative to the non-acidified treatments but the differences were not significant. The yields obtained for the digestate treatments ranged between 84.2% (D+NI) and 103.6% (D) of the yields produced by the same N rate from an inorganic source at HF. Advanced processing of digestate reduced N losses providing an environmentally sound option for N management.

Strategies to reduce nutrient pollution from manure management in China

“…Slurry acidification is being explored at the research scale to assess its potential to reduce NH 3 emission during storage [32] and processing, and after field application [33] . The co-benefits of slurry acidification can be reductions in methane emissions during slurry storage [34] , possibly because of inhibited methanogenesis in acidic conditions.…”

“…Since NH 3 emissions represent a significant agronomic loss of N following manure spreading, a range of mitigation strategies should be explored, including the use of shallow injection, trailing hose/shoe [45] and rapid incorporation. In addition, slurry acidification is known to reduce NH 3 emissions from liquid slurries and digestate [33,36] , so further information on the costs, practicalities and attitudes to this technology is needed for production systems in China. Although much of this NH 3 mitigation technology has been developed for large equipment in the EU, there is opportunity for smaller-scale spreading equipment to be developed that would be more suitable for the smaller land areas in China.…”

Dynamics of Different Buffer Systems in Slurries Based on Time and Temperature of Storage and Their Visualization by a New Mathematical Tool

“…Slurry which has been acidified to a pH of 5.5 may cut emissions of NH 3 by more than 75% and emissions of CH 4 by 94% [15]. Besides that, a 95% reduction in ammonia emissions were also found in acidified digestate [16]. In Denmark, the acidification of slurry is already a well-established method to lower emissions during the storage and application of slurry [17,18].…”

Combining Seed Dressing and Foliar Applications of Phosphorus Fertilizer Can Give Similar Crop Growth and Yield Benefits to Soil Applications Together With Greater Recovery Rates

“…The same soil and wheat variety was used for all trials. Further details of the soil chemical, biological and physical properties can be found in Sánchez-Rodríguez et al (2018). Seed dressings were applied to the seed coat using a micro-pipette and then air dried at 20 • C for 2 h before planting.…”