Animal production is a significant source of greenhouse gas (GHG) emissions worldwide. Depending on the accounting approaches and scope of emissions covered, estimates by various sources (IPCC, FAO, EPA or others) place livestock contribution to global anthropogenic GHG emissions at between 7 and 18 percent. The current analysis was conducted to evaluate the potential of nutritional, manure and animal husbandry practices for mitigating methane (CH4) and nitrous oxide (N2O) – i.e. non-carbon dioxide (non-CO2) – GHG emissions from livestock production. These practices were categorized into enteric CH4, manure management and animal husbandry mitigation practices. Emphasis was placed on enteric CH4 mitigation practices for ruminant animals (only in vivo studies were considered) and manure mitigation practices for both ruminant and monogastric species. Over 900 references were reviewed; and simulation and life cycle assessment analyses were generally excluded. In evaluating mitigation practices, the use of proper units is critical. Expressing enteric CH4 energy production on gross energy intake basis, for example, does not accurately reflect the potential impact of diet quality and composition. Therefore, it is noted that GHG emissions should be expressed on a digestible energy intake basis or per unit of animal product (i.e. GHG emission intensity), because this reflects most accurately the effect of a given mitigation practice on feed intake and the efficiency of animal production. EntErIC CH4 MItIgAtIon prACtICEs Increasing forage digestibility and digestible forage intake will generally reduce GHG emissions from rumen fermentation (and stored manure), when scaled per unit of animal product, and are highly-recommended mitigation practices. For example, enteric CH4 emissions may be reduced when corn silage replaces grass silage in the diet. Legume silages may also have an advantage over grass silage due to their lower fibre content and the additional benefit of replacing inorganic nitrogen fertilizer. Effective silage preservation will improve forage quality on the farm and reduce GHG emission intensity. Introduction of legumes into grass pastures in warm climate regions may offer a mitigation opportunity, although more research is needed to address the associated agronomic challenges and comparative N2O emissions with equivalent production levels from nitrogen fertilizer. Dietary lipids are effective in reducing enteric CH4 emissions, but the applicability of this practice will depend on its cost and its effects on feed intake, production and milk composition. High-oil by-product feeds, such as distiller’s grains, may offer an economically feasible alternative to oil supplementation as a mitigation practice, although their higher fibre content may have an opposite effect on enteric CH4, depending on basal diet composition. Inclusion of concentrate feeds in the diet of ruminants will likely decrease enteric CH4 emissions per unit of animal product, particularly when above 40 percent of dry matter intake. The effect may depend on type of ‘concentrate’ inclusion rate, production response, impact on fibre digestibility, level of nutrition, composition of the basal diet and feed processing.

Mitigation of greenhouse gas emissions in livestock production - A review of technical options for non-CO2 emissions

A replicate long-term experiment was conducted using anaerobic digestion (AD) as a model process to determine the relative role of niche and neutral theory on microbial community assembly, and to link community dynamics to system performance. AD is performed by a complex network of microorganisms and process stability relies entirely on the synergistic interactions between populations belonging to different functional guilds. In this study, three independent replicate anaerobic digesters were seeded with the same diverse inoculum, supplied with a model substrate, α-cellulose, and operated for 362 days at a 10-day hydraulic residence time under mesophilic conditions. Selective pressure imposed by the operational conditions and model substrate caused large reproducible changes in community composition including an overall decrease in richness in the first month of operation, followed by synchronised population dynamics that correlated with changes in reactor performance. This included the synchronised emergence and decline of distinct Ruminococcus phylotypes at day 148, and emergence of a Clostridium and Methanosaeta phylotype at day 178, when performance became stable in all reactors. These data suggest that many dynamic functional niches are predictably filled by phylogenetically coherent populations over long time scales. Neutral theory would predict that a complex community with a high degree of recognised functional redundancy would lead to stochastic changes in populations and community divergence over time. We conclude that deterministic processes may play a larger role in microbial community dynamics than currently appreciated, and under controlled conditions it may be possible to reliably predict community structural and functional changes over time.

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Deterministic processes guide long-term synchronised population dynamics in replicate anaerobic digesters.

http://sites.bsyse.wsu.edu/ndegwa/main/publications/downloads/Publication%20list/Article%209.pdf

A review of ammonia emission mitigation techniques for concentrated animal feeding operations

Agriculture is one of the economic sectors that affect climate change contributing to greenhouse gas emissions directly and indirectly. There is a trend of agricultural greenhouse gas emissions reduction, but any practice in this direction should not affect negatively farm productivity and economics because this would limit its implementation, due to the high global food and feed demand and the competitive environment in this sector. Precision agriculture practices using high-tech equipment has the ability to reduce agricultural inputs by site-specific applications, as it better target inputs to spatial and temporal needs of the fields, which can result in lower greenhouse gas emissions. Precision agriculture can also have a positive impact on farm productivity and economics, as it provides higher or equal yields with lower production cost than conventional practices. In this work, precision agriculture technologies that have the potential to mitigate greenhouse gas emissions are presented providing a short description of the technology and the impacts that have been reported in literature on greenhouse gases reduction and the associated impacts on farm productivity and economics. The technologies presented span all agricultural practices, including variable rate sowing/planting, fertilizing, spraying, weeding and irrigation.

Precision Agriculture Technologies Positively Contributing to GHG Emissions Mitigation, Farm Productivity and Economics

The goal of this review was to analyze published data on animal management practices that mitigate enteric methane (CH4) and nitrous oxide (N2O) emissions from animal operations. Increasing animal productivity can be a very effective strategy for reducing greenhouse gas (GHG) emissions per unit of livestock product. Improving the genetic potential of animals through planned cross-breeding or selection within breeds and achieving this genetic potential through proper nutrition and improvements in reproductive efficiency, animal health, and reproductive lifespan are effective approaches for improving animal productivity and reducing GHG emission intensity. In subsistence production systems, reduction of herd size would increase feed availability and productivity of individual animals and the total herd, thus lowering CH4 emission intensity. In these systems, improving the nutritive value of low-quality feeds for ruminant diets can have a considerable benefit on herd productivity while keeping the herd CH4 output constant or even decreasing it. Residual feed intake may be a tool for screening animals that are low CH4 emitters, but there is currently insufficient evidence that low residual feed intake animals have a lower CH4 yield per unit of feed intake or animal product. Reducing age at slaughter of finished cattle and the number of days that animals are on feed in the feedlot can significantly reduce GHG emissions in beef and other meat animal production systems. Improved animal health and reduced mortality and morbidity are expected to increase herd productivity and reduce GHG emission intensity in all livestock production systems. Pursuing a suite of intensive and extensive reproductive management technologies provides a significant opportunity to reduce GHG emissions. Recommended approaches will differ by region and species but should target increasing conception rates in dairy, beef, and buffalo, increasing fecundity in swine and small ruminants, and reducing embryo wastage in all species. Interactions among individual components of livestock production systems are complex but must be considered when recommending GHG mitigation practices.

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Special topics--Mitigation of methane and nitrous oxide emissions from animal operations: III. A review of animal management mitigation options.

Ammonia, methane, and carbon dioxide are the primary atmospheric emissions from cattle and pig farms. A
significant part of these emissions is produced by the decomposition of slurry organic matter during manure storage and
treatment phases. Present solutions to contain emissions from storage lagoons generally involve reducing the free surface of
the slurry by covering it either with permanent fixed structures or temporary floating ones. This study investigated the
effectiveness of five simple floating covers in reducing emissions from pig and cattle slurry. The coverings included vegetable
oil (a mixture of rapeseed and soybean oil), expanded clay, chopped maize stalks, chopped wheat straw, and chopped wood
chips. All were tested at two different thicknesses: 70 and 140 mm for solid coverings, and 3 and 9 mm for liquid. Slurry
samples covered with the above-mentioned materials were placed in nine stainless steel airtight cylinders measuring 190 dm3.
Gaseous and odor concentrations in the headspace were monitored using a Bruel & Kjaer 1302 multi-gas monitor and a T07
olfactometer. The flotation aptitude of the different coverings was also tested. Results revealed substantial differences in
ammonia emission reduction efficiency (1% to 100%) and odor abatement (0% to 90%), and high levels of reduction efficiency
were achieved by all the tested covers at the higher thickness. However, equally valid results were not obtained for methane
emissions reduction. In regard to flotation aptitude and cover deterioration on slurry, expanded clay and wood chips
demonstrated long-term resistance to both deterioration and sinking.

Evaluation of simplified covering systems to reduce gaseous emissions from livestock manure storage

Global warming is linked to the reduction of green house gas emissions (GHG). The anaerobic digestion of animal manure and energy crops is a promising way of reducing GHG emissions. The increasing number of biogas plants involves a high consumption of energy crops and the needed of big agricultural area. In Italy, cereals silages are the main feedstock for biogas production and are commonly grown under two different crop systems: single crop (only maize) and double crops (maize later winter cereals). In this paper we present the results of experimental field tests carried out by monitoring the anaerobic biomethane potential (BMP) of different cereals silages commonly grown in the Padanian Plan. A laboratory device has been developed to measure the specific biomethane production of the different cereal silages. The different energy crops have been evaluated, in single and double crop systems, expressing the biomethane production per hectare. The maize hybrids show higher specific biomethane potentials respect to winter cereals. Maize FAO class 700 achieves the highest production per hectare as a single crop. Nevertheless, the highest biomethane productions per hectare are reached with double crop system in particular when maize FAO class 500 follows triticale (+12% respect the best single crop system).

Biomethane production from different crop systems of cereals in Northern Italy.

Used as alternative energy sources, solid biofuels have the advantage of simultaneously reduce fossil fuel dependence and mitigate climate changes by reducing greenhouse gas emissions. Biomass storage and handling play a key role for wood fuel quality assessment: in particular, the presence of covering systems influences biomass drying process and factors leading to bulk compaction (e.g. reduced particle size) negatively affect woody biomass preservation till final use. To study the effect that particle size and covering have on biofuel quality, Short Rotation Forestry (SRF) poplar trees were harvested and chipped by means of a Claas Jaguar 890 operating machine equipped with a “GBE-1” header for SRF. The chipping procedure was carried out in March 2009 using on the same header both the standard chipping drum and a special on purpose drum designed by CRA-ING to obtain coarser particles. The chipped biomass was subsequently stored in stacks on a paved surface for a 120 days period to evaluate: i) effect of particle size on uncovered stacks drying dynamic and fuel quality, ii) effect of the presence of non-woven tarp on drying and fuel quality of biomasses standardly chipped with the conventional drum. Coarser stack was found to have a less prompt dehydration and, at the end of the storage period, have less energy and dry matter loss. In case of biomass chipped with the conventional drum, at the end of the storage period the effect of covering ended up in wood fuel with significantly higher heating value.

Poplar wood chip storage: effect of particle size and breathable covering on drying dynamics and biofuel quality.

BACKGROUND: Much research has been done on biochemical methane potential (BMP) determinations. However, although anaerobic digestion for methane production is driven by microorganisms, little information is available on the microbial community response to different organic residues. The aim of this study was to characterize the microbial communities during the treatment of different organic matrices.



RESULTS: BMP were comparable for energy crops and several agro-industrial biomasses. Denaturing gradient gel electrophoresis (DGGE) showed the dominance of clostridia and Methanosarcina. Principal component analyses of PCR-DGGE profiles indicated microbial shifts between the start and end of the processes. Microbial communities showed similar structures that, in particular for Archaea, clustered together independently of the nature of the matrix treated. Bacterial communities were richer, more dynamic and even than archaeal ones. Real-time quantitative PCR revealed that the Methanosarcinales dominated the archaeal community while sulphate-reducing bacteria were present at low titers. A statistically significant correlation indicated that more even archaeal communities were associated with higher BMP.



CONCLUSION: Different shifts occurred between Archaea and Bacteria exposed to different matrices treated by anaerobic digestion. While bacterial communities varied relatively widely, convergent archaeal community structures were selected in response to different biomasses treated. Copyright © 2012 Society of Chemical Industry

Massimo Brambilla

Papers

Evaluation of simplified covering systems to reduce gaseous emissions from livestock manure storage

Biomethane production from different crop systems of cereals in Northern Italy.

Poplar wood chip storage: effect of particle size and breathable covering on drying dynamics and biofuel quality.

Shifts of microbial community structure during anaerobic digestion of agro-industrial energetic crops and food industry byproducts

Foliar and root uptake of 134Cs, 85Sr and 65Zn in processing tomato plants (Lycopersicon esculentum Mill.).