Slurry storage is a significant source of NH₃ and greenhouse gas (GHG) emissions. The aim of this laboratory study was to assess the effects of different chemical additives and biochars on the emissions of NH₃, N₂O, CO₂, and CH₄ during the short-term storage of pig slurry. The experiment was performed using Kilner jars filled with raw slurry as control and six treatment additives (5% w/w): acidified slurry, alkalinized slurry, neutralized slurry, agroforestry biochar, cardoon biochar, and elderberry biochar. The gas emissions were measured for 30 days, and the composition of the slurries was determined. During short-term storage, the results of this laboratory study indicated that the NH₃ emissions were reduced by 58% by acidification and by 20% by the biochars (Agroforestry, Cardoon, and Elderberry treatments), while neutralization reduced this loss by only 12%. Nitrous oxide emissions were not reduced by the chemical additives (Acidified, Alkalinized, and Neutralized treatments), while this loss was increased by 12% by the biochars. Carbon dioxide, CH₄, and global warming potential emissions were not affected by the chemical additives and biochars. Furthermore, the absence of differences between the biochars may be related to their similar composition. Regarding the influence of the studied additives on NH₃ losses, it can be concluded that acidification was the best mitigation measure and the biochars were quite similar due to their composition. Furthermore, neutralization had the advantage of sanitizing the slurry, but only had a mild impact on NH₃ preservation.

The storage of animal manure is a major source of gaseous emissions. The aim of this study was to evaluate the effects of biochar and clinoptilolite on the composition and gaseous emissions during the storage of separated liquid fraction of pig slurry. The experiment was carried out using containers with 6 L of pig slurry each. The additives biochar and clinoptilolite were added alone and mixed to the pig slurry at a rate of 2.5% each, in a total of four treatments with three replicates including the control. Gaseous emissions were monitored by a photoacoustic multigas monitor, and slurry samples were collected at 0 and 85 days and their composition assessed. Results showed that the addition of biochar could modify the physicochemical properties of the slurry. The addition of biochar did not reduce the E. coli during the experiment while clinoptilolite decreased its prevalence. The addition of biochar or clinoptilolite reduced significantly the NH₃ emission during the storage of slurry, but no advantages were gained with their combination. The addition of biochar significantly reduced the CO₂ and CH₄ emissions relative to clinoptilolite, however N₂O emissions and global warming potential did not differ among the additives. We conclude that the biochar and clinoptilolite are recommended as a mitigation measure to reduce gaseous emissions and preserve the fertiliser value at slurry storage.

The treatment of animal slurry is used to improve management on a farm scale. The aim of this laboratory study was to assess the effects of the addition of the additives biochar, alum and clinoptilolite before the mechanical separation of whole pig slurry (WS) on the characteristics and emission of NH₃, N₂O, CO₂ and CH₄ from solid (SF) and liquid fractions (LF). The additives were mixed with WS (5% w/w), followed by separation, in a total of 12 treatments with 3 replicates, including the controls and WS with additives. Gaseous emissions were measured for 30 d by a photoacoustic multigas monitor, and initial characteristics of the slurries were assessed. The results indicated that the separation of the WS modified the initial physicochemical characteristics and increased the GWP emissions of the SF and LF, but not the NH₃ losses. However, the addition of additives before separation increased the nutrient value and reduced the GWP emissions from the SF and LF. Additionally, just the additive alum was effective in the reduction of E. coli. The additives led to significant reductions in NH₃ and N₂O emissions, with higher reductions in NH₃ losses for alum (51% for NH₃) and similar N₂O losses for all additives (70% for N₂O) observed, whereas the CO₂ and CH₄ emissions were reduced by biochar (25% for CO₂ and 50% for CH₄) and alum (33% for CO₂ and 30% for CH₄) but not by clinoptilolite. Although the additives had a positive effect on slurry management, it can be concluded that the addition of alum before mechanical separation has the potential to be the best mitigation measure because it improves the nutrient content and sanitation and decreases gaseous losses from slurry management.

ISHS XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on Organic Horticulture: Productivity and Sustainability COVER CROPS AS NITROGEN SOURCE FOR ORGANIC FARMING IN SOUTHWEST EUROPE

Biofilters are an effective air pollution control technology to break down gaseous contaminants and produce innocuous end products. This laboratory study aimed to evaluate a biofilter media, mainly composed by tomato waste, as packing material to reduce NH₃, N₂O, CO₂ and CH₄ losses from stored pig slurry. Three mixtures of packing materials, with and without oxalic acid, were arranged in treatments, namely: mixture of tomato waste, pine bark and agricultural compost; mixture of tomato waste and rice husk; tomato waste only. A control treatment (no biofilter) was also included. The experiments were conducted using a system of laboratory scale biofilters connected to jars filled with pig slurry and under a constant airflow rate. The gas concentrations were measured for 14 days and the physicochemical of the packing materials were assessed. Results showed that biofilter media mixtures had a potential for NH₃ retention ranging from 51 to 77% and the addition of oxalic acid to these biofilters increased NH₃ retention to 72–79%. Additionally, the biofilter media mixtures with and without oxalic acid showed a potential retention for CH₄ (29–69%) but not for N₂O, yet with no impact on the global warming potential. It can be concluded that tomato based biofilters had the potential to reduce gaseous emissions from slurry.

Composting is one of the best organic waste management techniques, with zero waste; however, it generates environmental impacts. The objective of this study was to evaluate the emission of NH₃, N₂O, CO₂, and CH₄ from the composting of olive, elderberry, and grape agro-food waste. The experiment was carried out using reactors receiving straw as control and three treatments receiving mixtures of straw and olive, elderberry, or grape wastes. The gas emissions were measured for 150 days, and the composition of the mixtures and composts was determined. The results showed NH₃ and CH₄ emissions were reduced by 48% and 29% by the Olive and Elderberry treatments, while only NH₃ loss was reduced by 24% by the Grape treatment. Nitrous oxide, CO₂, and GWP emissions were reduced by 46%, 32%, and 34% by the Olive treatment, while these losses were not reduced by the Elderberry or Grape treatments. It can be concluded olive waste can effectively reduce NH₃ and GWP, while elderberry and grape wastes are also effective in reducing NH₃, but not GWP. Thus, the addition of agro-food waste appears to be a promising mitigation strategy to reduce gaseous losses from the composting process.