Greenhouse gas emissions from piggery and biogas digesters in the Red River Delta of Vietnam

High demand for pork consumption in Vietnam has led to a shift of pig production systems from smallholder to industrial-scale farms, particularly in the Red River Delta. This production intensification also produces massive manure and urine quantities, leading to water, air, and soil pollution. The use of biogas plants has been seen as efficient to achieve in the same time a decrease in pollution, and a provision of biogas resources and bio-organic fertilizers. However, increasing pig head density has been causing great pressure on biogas digesters, as their size is not big enough for treatments anymore. Inappropriate utilization and management of biogas digesters can not only cause losses from pig wastes, but also contributes to increase greenhouse gas (GHG) emissions such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). This case study aims to identify the role and contributions of biogas digesters to better manage the sources of GHG emissions from pig wastes for different types of pig farms. Four provinces of the Red River Delta were selected to test the pig waste management efficiency of biogas digesters and measure GHG emissions from these systems. The findings show that CO2, CH4 and N2O emission rates from pig manure are at least twice as much what is allowed under the Vietnam national technical regulation on ambient air quality. However, the GHGs emission rate does not significantly differ between smallholder and industrial-scale farms in the four surveyed provinces. Sampling position (between inside piggeries and outside the outlet of biogas digesters) did not affect significantly GHG emissions rate. These results confirm that the pig waste management of biogas digesters for both smallholder and industrial-scale pig farms is not efficient and that efforts need to be invested to mitigate GHG emissions in pig production. Reducing pig density per piggery is highly recommended. The modification of biogas digester structure to separate solid pig manure and urine should also be considered. Otherwise, the application of other alternative aerobic or anaerobic digestion technologies should also be encouraged and promoted. Biogas digesters in pig production have a significant role to play in Vietnam government’s mitigation strategies, as well as from the perspective of biosafety and animal husbandry policies

Kinematic and dynamic modelling for a class of hybrid robots composed of m local closed-loop linkages appended to an n-link serial manipulator

Recently, more and more hybrid robots have been designed to meet the increasing demand for a wide spectrum of applications. However, development of a general and systematic method for kinematic design and dynamic analysis for hybrid robots is rare. Most publications deal with the kinematic and dynamic issues for individual hybrid robots rather than any generalization. Hence, in this paper, we present a novel method for kinematic and dynamic modelling for a class of hybrid robots. First, a generic scheme for the kinematic design of a general hybrid robot mechanism is proposed. In this manner, the kinematic equation and the constraint equations for the robot class are derived in a generalized case. Second, in order to simplify the dynamic modelling and analysis of the complex hybrid robots, a Lemma about the analytical relationship among the generalized velocities of a hybrid robot system is proven in a generalized case as well. Last, examples of the kinematic and dynamic modelling of a newly designed hybrid robot are presented to demonstrate and validate the proposed method

Greenhouse gas emissions from piggery and biogas digesters in the north of Vietnam

Increases in pig farm densities have caused great pressures on waste management systems and produce massive manure and urine quantities in Vietnam. This study aimed to identify the role and contributions of biogas digesters to better manage the sources of greenhouse gas (GHG) emissions from pig wastes for different types of pig farms in the north of Vietnam. Four provinces, namely Thanh Hoa, Phu Tho, Thai Binh, Vinh Phuc, were identified. A total of 24 farms were purposively selected including 16 small-size farms and 8 larger-size farms. The findings showed that GHG emissions from small-size farms (154.8 t CO2-eq.yr-1) did not significantly differ from the amounts measured in larger-size farms (139.1 t CO2-eq.yr-1) in the four surveyed provinces. The sampling position did not significantly affect the GHG emission rates, with 173.9 t CO2-eq.yr-1 inside piggeries and 120.8 t CO2-eq.yr-1 outside the outlet of the biogas digesters (p-value=0.09). N2O emissions require further measurements at different farm sizes and sites. These results confirmed that the pig waste management of biogas digesters for both small-size and larger-size pig farms is not completely efficient and that efforts need to be invested in to mitigate GHG emissions in pig production. Reducing pig density per piggery is highly recommended. The application of other alternative aerobic or anaerobic digestion technologies like vermicompost, effective microorganisms, and composting should also be encouraged and promoted