The potential of dairy manure and sewage management pathways towards a circular economy: A meta-analysis from the life cycle perspective

A systematic review of life-cycle GHG emissions from intensive pig farming: Accounting and mitigation

Pork accounts for approximately 35 % of the global meat supply, with approximately 747 million tons of CO2e greenhouse gas (GHG) emissions annually. To meet the increasing demand for pork, intensive farming is becoming the priority rearing system owing to its higher productivity. Given the climate transformation ambitions of the pig industry but the lack of knowledge and data, we conducted a systematic review of studies published in the period of 2010-2022 from a life-cycle perspective, with a focus on greenhouse gas emissions accounting and mitigation. The significant variations in systematic harmonized global warming intensities (GWIs) can be primarily attributed to differences in accounting approaches, activity data, technologies and geographical conditions. To understand more, we broke down the entire life cycle and revealed the underlying reasons for modelling mechanisms and data from the main emitters (e.g., feeding, pig rearing, and manure management). These findings are expected to support and improve the transparency, consistency, and comprehensiveness of life-cycle GHG emissions accounting in pig farming. Potential mitigation measures were also reviewed and discussed to provide insights to support the sustainable development of the pig industry.

Co-substrate composition is critical for enrichment of functional key species and for process efficiency during biogas production from cattle manure

Cattle manure has a low energy content and high fibre and water content, limiting its value for biogas production. Co-digestion with a more energy-dense material can improve the output, but the co-substrate composition that gives the best results in terms of degree of degradation, gas production and digestate quality has not yet been identified. This study examined the effects of carbohydrate, protein and fat as co-substrates for biogas production from cattle manure. Laboratory-scale semi-continuous mesophilic reactors were operated with manure in mono-digestion or in co-digestion with egg albumin, rapeseed oil, potato starch or a mixture of these, and chemical and microbiological parameters were analysed. The results showed increased gas yield for all co-digestion reactors, but only the reactor supplemented with rapeseed oil showed synergistic effects on methane yield. The reactor receiving potato starch indicated improved fibre degradation, suggesting a priming effect by the easily accessible carbon. Both these reactors showed increased species richness and enrichment of key microbial species, such as fat-degrading Syntrophomonadaceae and families known to include cellulolytic bacteria. The addition of albumin promoted enrichment of known ammonia-tolerant syntrophic acetate- and potential propionate-degrading bacteria, but still caused slight process inhibition and less efficient overall degradation of organic matter in general, and of cellulose in particular.

Bismuth impregnated biochar for efficient uranium removal from solution: Adsorption behavior and interfacial mechanism

In this work, Bi₂O₃ doped horse manure-derived biochar was obtained by carbonizing the H₂O₂-modified horse manure loaded with bismuth nitrate under nitrogen atmosphere at 500 °C. The results showed that there was a sharp response between the as-prepared bismuth impregnated biochar and uranium(VI) species in solution, which resulted in a short equilibrium time (<80 min), a fast adsorption rate (about 5.0 mg/(g·min)), a high removal efficiency (93.9%) and a large adsorption capacity (516.5 mg/g) (T = 298 K, pH = 4, C_i = 10 mg/L and m/V = 0.1 g/L). Besides, the removal behavior of the bismuth impregnated biochar for uranium(VI) did not depend on the interfering ions and ion strength, except Al³⁺, Ca²⁺, CO₃^2- and PO₄^3-. These results indicated that the modified biochar might possess the potential of remediating the actual uranium(VI)-containing wastewater. Moreover, the interaction mechanism between Bi₂O₃ doped biochar and uranium(VI) species was further explored. The results demonstrated that the enrichment of uranium(VI) on the surface of the as-prepared biochar was controlled by various factors, such as surface complexation, ion exchange, electrostatic attraction, precipitation and reduction, which facilitated the adsorption of uranium(VI) on the bismuth impregnated biochar.

Does policy cognition affect livestock farmers' investment in manure recycling facilities? Evidence from China

An increase in living standards and dietary changes have induced a rapid growth in the livestock sector worldwide, which has led to considerable environmental damages due inappropriate disposal of livestock manure. Using primary data from a field survey of cattle farmers in China, this paper empirically examines the impact of policy cognition on livestock farmers' investment in manure recycling facilities. The impact is tested through the multiple mediator model to accommodate two potential mediating mechanisms, which are the agricultural cooperative membership and land leasing. Three conclusions arise. First, policy cognition has a significant positive impact on both the diversification and amounts of farmers' investment in manure recycling facilities. Second, membership in agricultural cooperatives and participation in land leasing are two important mediating mechanisms for policy cognition to affect farmers' investment decisions on manure recycling. Finally, for the two mediating variables, leasing additional agricultural land promotes more investment in manure recycling facilities, but less in investment diversification, while cooperative membership has the opposite impact. This study contributes to three areas of literature on the factors affecting investment decisions, the mediating effects of policy cognition and the investment in non-production related assets. Regarding policy implications, we identify the importance of promoting policy awareness and agricultural cooperatives among livestock farmers, as well as developing land lease markets in agricultural regions in promoting investment in manure recycling facilities.