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Carbon emission reduction and carbon neutrality have become the global concern. Livestock and poultry manure is an important emission source of non-CO2 high-strength GHGs, such as N2O and CH4. Modern livestock and poultry production driven by population growth and society development accounts one third carbon emission in China’s agriculture. Excavating its carbon reduction potential is as important as resources recycling and valorization for manure managemen
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● Carbon reduction potential of manure treatment technologies was summarized. ● Accounting methodologies of carbon emission and footprint of manure were analyzed. ● The quote of carbon trading market at home and abroad was analyzed. ● Some points for the boost of potential of manure carbon trading were advised.
The rapid growth of the livestock and poultry production in China has led to a rise in manure generation, which contributes to the emissions of GHGs (greenhouse gases including CH4, N2O and CO2) and other harmful gases (NH3, H2S). Reducing and managing carbon emissions has become a critical global environmental imperative due to the adverse impacts of GHGs. Unlike previous reviews that focused on resource recovery, this work provides an unique insight of transformation from resource-oriented manure treatment to integration of resource recovery with pollution reduction, carbon accounting and trading, focusing on the sustainable development of manure management system. Considering the importance of accounting methodologies for carbon emission and trading system toward carbon neutrality society, suggestions and strategies including attaching high importance to the development of more accuracy accounting methodologies and more practical GHG emission reduction methodologies are given in this paper. This work directs the establishment of carbon reduction methodologies and the formulation of governmental policies for livestock and poultry manure management system in China.
● An automatic weighing system for monitoring bodyweight of broilers was developed. ● The new system was compared to the established live-bird sales weighing system data and tested in various conditions. ● The system demonstrated superior accuracy and stability for commercial houses.
Bodyweight is a key indicator of broiler production as it measures the production efficiency and indicates the health of a flock. Currently, broiler weight (i.e., bodyweight) is primarily weighed manually, which is time-consuming and labor-intensive, and tends to create stress in birds. This study aimed to develop an automatic and stress-free weighing platform for monitoring the weight of floor-reared broiler chickens in commercial production. The developed system consists of a weighing platform, a real-time communication terminal, computer software and a smart phone applet user-interface. The system collected weight data of chickens on the weighing platform at intervals of 6 s, followed by filtering of outliers and repeating readings. The performance and stability of this system was systematically evaluated under commercial production conditions. With the adoption of data preprocessing protocol, the average error of the new automatic weighing system was only 10.3 g, with an average accuracy 99.5% with the standard deviation of 2.3%. Further regression analysis showed a strong agreement between estimated weight and the standard weight obtained by the established live-bird sales system. The variance (an indicator of flock uniformity) of broiler weight estimated using automatic weighing platforms was in accordance with the standard weight. The weighing system demonstrated superior stability for different growth stages, rearing seasons, growth rate types (medium- and slow-growing chickens) and sexes. The system is applicable for daily weight monitoring in floor-reared broiler houses to improve feeding management, growth monitoring and finishing day prediction. Its application in commercial farms would improve the sustainability of poultry industry.
● NH3 dispersion from a multi-floor pig building was compared to a single-floor building. ● NH3 dispersed much further from the multi-floor pig building. ● Wind speed, direction and source concentration were important for NH3 dispersion. ● NH3 tended to accumulate in the east and west yards of the multi-floor pig building. ● Higher wind speed was the likely cause of more NH3 accumulation in the yards.
Multi-floor buildings for raising pigs have recently attracted widespread attention as an emerging form of intensive livestock production especially in eastern China, due to the fact that they can feed a much larger number of animals per unit area of land and thus alleviate the shortage of land available for standard single-floor pig production facilities. However, this more intensive kind of pig building will pose new challenges to the local environment in terms of pollutant dispersion. To compare the dispersion air pollutants (ammonia as a representative) emitted from multi- versus single-floor pig buildings, ammonia dispersion distance and concentration gradients were investigated through three-dimensional simulations based on computational fluid dynamics. The validation of an isolated cubic model was made to ensure the simulation method was effective. The effects of wind direction, wind speed and emission source concentration at 1.5 m (approximate human inhalation height) during summer were investigated. The results showed that the ammonia dispersion distance of the multi-floor pig building was far greater than that of the single-floor building on a plane of Z = 1.5 m. When the wind direction was 67.5°, the wind speed was 2 m·s−1 and the emission source concentration was 20 ppmv, the dispersion distance of the multi-floor pig building could reach 1380 m. Meanwhile, the ammonia could accumulate in the yard to 7.68 ppmv. Therefore, future site selection, wind speed and source concentration need to be given serious consideration. Based on the simulation used in this study with source concentration is 20 ppmv, the multi-floor pig buildings should be located 1.4 km away from residential areas to avoid affecting residents. The results of this study should guidance for any future development of multi-floor pig buildings.
● Microbial fermentation in the rumen is a main source of methane emissions. ● Nutritional strategies can effectively mitigate methane emissions by manipulating biochemical reactions in the methanogenesis pathways. ● Mitigation practices must be evaluated in an integrated animal production system instead of as isolated components.
Within the agricultural sector, animal production contributes to 14.5% of global anthropogenic greenhouse gas emissions and produces around 37% of global CH4 emissions, mainly due to ruminal fermentation in ruminants. Over 90% of CH4 is synthesized by methanogens in the rumen during carbohydrate fermentation. According to different substrates, methanogenesis pathways can be divided into four categories: (1) hydrogenotrophic pathway; (2) acetoclastic pathway; (3) methyl dismutation pathway; and (4) methyl-reducing pathway. Based on the principle of biochemical reactions in the methanogenesis pathways, this paper reviews the latest publications on CH4 decreases in ruminants and described three nutritional strategies in terms of dietary nutrient manipulation (feeding management, feed composition, forage quality and lipids), microbial manipulation (ionophore, defaunation, methanogen inhibitors and probiotics), and chemical manipulation (nitrate, organic acids, plant secondary metabolites and phlorotannins, or halides in seaweeds). For each mitigation strategy, the review discusses effectiveness for decreasing CH4 emissions, application prescription, and feed safety based on results from in vitro and in vivo studies. This review summarizes different nutritional strategies to mitigate CH4 emissions and proposed comprehensive approaches for future feeding interventions and applications in the livestock industry.
● Methane production from fresh straw was 7.50% higher than dry straw. ● The structure of fresh straw was more conducive to be degraded. ● Organic components of fresh straw was richer and higher than dry straw. ● Clostridium_sensu_stricto_1 , Sporosarcina and Methanosarcinia dominated AD. ● Metagenomics revealed Metanosarcinia adapted to high VFA stress via multiple pathways.
Dry corn straw (DCS) is usually used in anaerobic digestion (AD), but fresh corn straw (FCS) has been given less consideration. In this study, the thermophilic AD of single-substrate (FCS and DCS) and co-digestion (straw with cattle manure) were investigated. The results show that when FCS was used as the single-substrate for AD, the methane production was 144 mL·g−1·VS−1, which was 7.5% and 19.6% higher than that of single DCS and FCS with cattle manure, respectively. In addition, the structure of FCS was loose and coarse, which was easier to be degraded than DCS. At the hydrolysis and acidification stages, Clostridium_sensu_stricto_1, Clostridium_sensu_stricto_7 and Sporosarcina promoted the decomposition of organic matter, leading to volatile fatty acids (VFAs) accumulation. Methanosarcina (54.4%) activated multifunctional methanogenic pathways to avoid the VFAs inhibition, which was important at the CH4 production stage. The main pathway was hydrogenotrophic methanogenesis, with genes encoding formylmethanofuran dehydrogenase (K00200-K00203) and tetrahydromethanopterin S-methyltransferase (K00577-K00584). Methanosarcina also activated acetotrophic and methylotrophic methanogenesis pathways, with genes encoding acetyl phosphate (K13788) and methyl-coenzyme M reductase (K04480, K14080 and K14081), respectively. In the co-digestion, the methanogenic potential of FCS was also confirmed. This provides a scientific basis for regulating AD of crop straw.
● Integration of alkaline pretreatment and air mixing for co-digestion was validated. ● Alkaline pretreatment enhanced hydrolysis of poultry litter and wheat straw. ● Cumulative methane yield was improved by 46.7% compared to the control. ● The cone model best fitted the methane yield kinetics with R 2 ≥ 0.9979. ● Total volatile solids removal was improved by 2.3 times in the digestate.
Alkaline pretreatment (AL) and air mixing (air) both have the potential to improve anaerobic co-digestion (Co-AD) of poultry litter with wheat straw for methane production. In this study, the effects of the combination of AL (pH 12 for 12 h) and air mixing (12 mL·d−1) on the Co-AD process were investigated. The substrate hydrolysis was enhanced by AL, with soluble chemical oxygen demand increased by 4.59 times and volatile fatty acids increased by 5.04 times. The cumulative methane yield in the group of Co-AD by AL integrated with air (Co-(AL + air)), being 287 mL·(g VSadded)−1, was improved by 46.7% compared to the control. The cone model was found the best in simulating the methane yield kinetics with R2 ≥ 0.9979 and root mean square prediction error (rMSPE) ≤ 3.50. Co-(AL + air) had a larger hydrolysis constant k (0.14 d−1) and a shorter lag phase λ (0.99 d) than the control (k = 0.12 d−1, λ = 2.06 d). The digestate improved the removal of total solids and total volatile solids by 2.0 and 2.3 times, respectively. AL facilitated substrate degradation, while air can enrich the microbial activity, together enhancing the methane generation. The results show that AL + air can be applied as an effective method to improve methane production from the Co-AD process.
● Content of heavy metals in hydrochar varies considerably, from 50% to 100%. ● Concentrations of heavy metals in hydrochar can be higher than those in the dairy manure. ● Concentrations of heavy metals in hydrochar are far below the regulatory level.
Hydrochar produced from dairy manure is a regulated biosolid if being promoted for agricultural applications thus must have the properties that comply with all environmental standards and government regulations, including the levels of heavy metals (HMs). In this study, systematic research was conducted on HM levels in hydrochar from dairy manure and on the effects of processing conditions, including processing temperature (180–255 °C), holding time (30–120 min) and solid content of manure slurry (2%–15%), through a central composite design and statistical analyses. It was found that HMs can be retained in hydrochar, ranging from 40% to 100%. The processing temperature and solid content in the feed were the most influential process parameters that affected HMs retention in hydrochar. Statistical analysis showed that there was no single optimal point to minimize HMs retained in hydrochar, but there were minimization points at given processing time and solid content. Most HMs concentrations were higher in hydrochar than those initially in dairy manure but were greatly below the thresholds as set by the US government regulations. Thus, hydrochar is feasible for use as a phosphorus-enriched organic fertilizer and/or soil amendment for agricultural applications without serious concerns about HMs it might contain.
● Low-value biowaste including wood chip and potato peel was valorized to syngas. ● O2-blown co-gasification of wood chip and potato peel was simulated. ● Different reaction conditions on CCE, gas composition, and LHV were studied. ● Positive interaction between wood chip and potato peel in co-gasification was found.
Potato is the fifth largest agricultural crop in Canada and contributes to the generation of an abundant amount of potato peel. However, disposal/recycling this peel remains a challenge due to the stringent environmental regulations. Consequently, there is a lack of an appropriate recycling and valorization methods of potato peel. Gasification is an effective technology for producing syngas and an ecofriendly waste disposal approach. Syngas is an important industrial intermediate to produce synthetic fuels and chemicals. To develop an ecofriendly and cost-effective valorization approach for potato peel, this study used a mixture of woody biomass (i.e., wood chips) and potato peel to produce syngas by co-gasification using O2 as the gasifying agent at a constant equivalence ratio of 0.3 using Aspen Plus simulation software. The influences of gasification temperature and wood chip/potato peel weight ratio on the carbon conversion efficiency (CCE), and product gas composition (molar fraction) and lower heating value (LHV) of product gas were investigated. This simulation indicated that a positive synergistic interaction occurs between wood chips and potato peel in co-gasification process in terms of an increase in CCE by comparing the arithmetic value and real value at all simulated wood chip to potato peel weight ratios (44.9% to 85.8%, 46.5% to 76.2%, and 48.1% to 78.6% at ratios of 25:75, 50:50, and 75:25, respectively, for wood chips to potato peel). While the molar fraction of H2 and CO decreased continuously with increase in the weight percentage of wood chips in the wood chip-potato peel mixture from 0 wt% to 100 wt% (H2, at 42.1 mol% to 41.4 mol%; and CO at 44.0 mol% to 40.4 mol%), accompanied by a decrease of the LHV of the product gas (10.3 to 9.78 MJ·Nm−3). The study concluded that co-gasification for producing syngas is feasible and environmental-friendly option to recycle and valorize potato peel.
● Gasification of cow dung was evaluated using Aspen Plus software. ● Optimum reaction conditions were utilized to maximize hydrogen production. ● Steam gasification can effectively increase hydrogen production. ● Optimum hydrogen production was achieved at 800 °C and steam/biomass of 1.5 and 0.1 MPa.
In this study, a biomass gasification model was developed and simulated based on Gibbs free energy minimization by using software Aspen Plus. Two reactors, RYIELD and RGIBBS, were moslty used. The biomass feedstock used was cow dung. The model was validated. The composition, H2/CO ratio and low heating value (LHV) of the resulting synthetic gas (also known as syngas) was estimated by changing the operating parameters of gasification temperatures, steam and biomass ratios and pressures. Simulation results showed that increased gasification temperature helped to elevate H2 and CO content and H2 peaked at 900 °C. When steam increased as the gasification agent, H2 production increased. However, the steam/biomass (S/B) ratio negatively affected CO and CH4, resulting in lower LHV. The optimal S/B ratio was 1.5. An increase in pressure lead to a decrease in H2 and CO content, so the optimal pressure for gasification was 0.1 MPa.
● Simultaneous H2S and CO2 removal from biogas is studied. ● Renewable absorbent from biogas slurry is used in membrane contactor. ● More than 98% of H2S can be removed by membrane absorption. ● The impurities have less influence on H2S removal efficiency.
Upgrading biogas into biomethane not only improves the biogas utilization as vehicle fuel or natural gas substitute, but also reduces the greenhouse gases emissions. Considering the principle of engineering green energy process, the renewable aqueous ammonia (RAA) solution obtained from biogas slurry was used to remove H2S and CO2 simultaneously in the hollow fiber membrane contactor. RAA was mimicked in this study using the ammonia aqueous solution mixed with some typical impurities including ethanol, acetic acid, propionic acid, butyric acid and NH4HCO3. Compared with the typical physical absorption (i.e., pure water) removing 48% of H2S from biogas, RAA with 0.1 mol·L−1 NH3 could remove 97% of H2S. Increasing the NH3 concentration from 0.1 to 0.5 mol·L−1 could elevate the CO2 absorption flux from 0.97 to 1.72 mol·m−2·h−1 by 77.3%. Among the impurities contained in RAA, ethanol has a less impact on CO2 absorption, while other impurities like CO2 and acetic acid have significant negative impacts on CO2 absorption. Fortunately, the impurities have a less influence on H2S removal efficiency, with more than 98% of H2S could be removed by RAA. Also, the influences of operating parameters on acid gases removal were investigated to provide some engineering suggestions.
● LFD was treated by fly ash-based chemical precipitation and CO2 mineralization. ● > 93% COD and > 98% TP removal efficiency, and < 2 mS·cm−1 EC was achieved. ● COD and TP removal was achieved by co-precipitation during CO2 mineralization. ● CO2 mineralization neutralized the alkaline LFD and removed heavy met.
Chemical precipitation is a widely applied approach for a liquid fraction of digestate (LFD) of agricultural waste but its large-scale application requires low-cost and efficient precipitating agents and novel process design. This study evaluated novel approach for the efficient removal of contaminants from the LFD using fly ash-based chemical precipitation, followed by filtration and CO2 mineralization. The technical feasibility of this approach was evaluated using pH and electrical conductivity (EC), and removal efficiencies of total phosphorus (TP), chemical oxygen demand (COD) and heavy metals during the treatment. The fly ash used in this study showed a promising performance as a chemical precipitation agent for COD and TP removal from the treated LFD involving complex effects of precipitation and adsorption. CO2 bubbling after fly ash-based chemical precipitation provided further COD and TP removal by carbonation reactions between CO2 and the excessive alkaline minerals in fly ash. Although addition of fly ash to untreated LFD increased pH from 8.3 to 12.9 and EC from 7.01 to 13.7 mS·cm−1, CO2 bubbling helped neutralize the treated LFD and reduce the EC, and concentrations of toxic ions by carbonation reactions. The fly ash-based chemical precipitation and CO2 mineralization had > 93% COD and > 98% TP removal efficiencies, and resulted in an EC of < 2 mS·cm−1 and a neutral pH in the treated LFD, as well as the high purity calcite product.
● Titanate NFs were synthesized and photodegraded liquid digestate for the first time. ● The long titanate NFs (bandgap of 3.16 eV) have a high VFA removal rate of 72.9%. ● RSM has been used to optimize the VFA, COD, and color removal rate. ● The quadratic model and the effects of photocatalytic dosage were significant.
Titanate nanofibers (TNFs) were synthesized using a hydrothermal method and were employed for the first time in this study to photocatalytically degrade organic pollutants found in flocculated liquid digestate of poultry litter. The photocatalytic performance of TNFs, with a bandgap of 3.16 eV, was tested based on degradation of organic pollutants and removal of color. Five combinations of pollutant concentration and pH were examined (0.2 to 1.3 g·L−1 at pH 4 to 10). Central composite design (CCD) and response surface methodology (RSM) were applied in order to optimize the removal rates of volatile fatty acids (VFA) and chemical oxygen demand (COD), and the decolorization rate. There were no significant differences between the regression models generated by the CCD/RSM and the experimental data. It was found that the optimal values for pH, dosage, VFA removal rate, COD removal rate and decolorization rate were 6.752, 0.767 g·L−1, 72.9%, 59.1% and 66.8%, respectively. These findings indicates that photocatalytic TNFs have potential for the posttreatment of anaerobic digestion effluent, as well as other types of wastewater.
