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Woodchips in stand-off pads for wintering cows have been applied in countries like Ireland and New Zealand. Their primary role is to protect soils by effectively filtering nutrients during wet conditions, while ensuring a healthy and comfortable environment for the cows. The stand-off pad concept has the potential to be adopted in Canada to provide year-long outdoor access to tie-stall dairy cows. The objective of this study was to evaluate the effect of alternative filtering materials and bed aeration under controlled laboratory conditions. Twelve biofilter columns (0.3 m in diameter and 1-m high) were installed in 12 environmentally-controlled chambers (1.2-m wide by 2.4-m long), and divided into four treatments: a bed of conventional woodchips or an alternative mix of organic materials (sphagnum peat moss, woodchips and biochar) with and without aeration (flux rate set at 0.6 m3/min/m2). Approximately 0.6 L of semi-synthetic dairy manure and 1 L of tap water were poured on the biofilters during two experimental periods of 4 weeks, simulating the effect of either winter or summer conditions (room temperature below or over 10 °C) on the retention of nutrients and fecal bacteria. Results showed that the alternative biofilters under both summer and winter conditions were more efficient in removing COD, SS, TN, and NO 3 –N than conventional biofilters (maximum efficiencies of 97.6%, 99.7%, 96.4%, and 98.4%, respectively). Similarly for E. coli , they achieved a minimum concentration of 1.8 Log 10 CFU/100 ml. Conventional biofilters were more efficient for PO 4 –P removal with a maximum efficiency of 88.2%. Aeration did not have any significant effect under the tested temperature conditions. Additional factors such as media adaptation time as well as aeration flow during this period should be considered. • Stand-off pads have the potential to be adopted in Canada to provide year-long outdoor access to tie-stall dairy cows. • A filtering mixture of sphagnum peat moss, woodchips and biochar was more efficient in filtration capacities. • Woodchip filters showed to have greater phosphorus removal. • Aeration did not improve filtration capacities of filters. [ABSTRACT FROM AUTHOR]

Pyrolysis is the thermochemical decomposition of biomass under oxygen-limiting conditions used for biochar and bio-oil production. Depending on biomass feedstock, pyrolysis technology and operating parameters, product yields and properties will differ. Among the available pyrolysis units, auger pyrolysis is a polyvalent and promising technology for producing both bio-oil and biochar. These reactors are simple to operate and can be mobile, they require little or no carrier gas and low energy. Moreover, the operating parameters can be controlled easily in order to obtain the desired products. Recently, many research articles on biomass pyrolysis in auger reactors have been published. Design of laboratory-scale pyrolysis units and operating parameters differ considerably. Therefore, there was a need to list the studies in which auger pyrolysis reactors are used and to collect data for experimental operating parameters and product yields. The type and the capacity of the reactor, pyrolysis temperature, solid residence time, carrier gas flowrate, vapour residence time, and biomass feedstock type and size were identified as the parameters having the most influence on product yields and their properties. Because each pyrolysis reactor is unique, it is important to establish the relationship between operating parameters and product yields and their properties for each biomass feedstock. Future work is needed in order to provide simple solutions to scale-up laboratory-scale auger pyrolysis units to industrial size. [ABSTRACT FROM AUTHOR]

Biochar, a solid porous material obtained from the carbonization of biomass under low or no oxygen conditions, has been proposed as a climate change mitigation tool because it is expected to sequester carbon (C) for centuries and to reduce greenhouse gas (GHG) emissions from soils. This review aimed to identify key biochar properties and production parameters that have an effect on these specific applications of the biochar. Moreover, mechanisms involved in interactions between biochar and soils were highlighted. Following a compilation and comparison of the characteristics of 76 biochars from 40 research studies, biochars with a lower N content, and consequently a higher C/N ratio (>30), were found to be more suitable for mitigation of N 2 O emissions from soils. Moreover, biochars produced at a higher pyrolysis temperature, and with O/C ratio <0.2, H/C org ratio <0.4 and volatile matter below 80% may have high C sequestration potential. Based on these observations, biochar production and application to the field can be used as a tool to mitigate climate change. However, it is important to determine the pyrolysis conditions and feedstock needed to produce a biochar with the desired properties for a specific application. More research studies are needed to identify the exact mechanisms involved following biochar amendment to soil. [ABSTRACT FROM AUTHOR]

Enhancing movement options for confined dairy cows, like in tie-stall housing, may boost natural behaviour and welfare. Yet, limited data exists on the environmental impact of both indoor and outdoor exercise areas. This study investigates the impact of exercise pen type on effluent properties and gas emissions during winter and/or summer conditions in a northern country such as Canada. Forty-five Holstein dairy cows were randomly assigned to three treatments: (1) no exercise [cows kept indoors with tie-stalls (TSs)]; (2) indoor exercise [access to a 28 m2 cow−1 indoor pen (IP) for 1.5 h d−1] and (3) outdoor exercise [access to a 28 m2 cow−1 outside nonaerated (OnAP) or aerated stand-off pad (OAP) for 1.5 h d−1]. The effluent composition of OnAP and OAP varied notably between seasons. In winter, OAP leachates showed higher biological oxygen demand (+89 %), pH (+1.2 units), ammonium (+96 %) and total solids (+50 %), lower faecal but higher total coliforms (−120 % and +20 %, respectively) than OnAP during summer. In addition, OAP presented higher biological and chemical oxygen demand (+80 %) than OnAP in both seasons. Both OAP and OnAP showed higher carbon dioxide emissions (+150 %) and lower methane emissions during summer (−200 %) than IP and TS. Nitrous oxide emissions were higher for OnAP (+600 %) than in OAP, IP and TS, with no changes in ammonia emissions across treatments. Outdoor exercise for dairy cows using a filtering pen didn't meet environmental limits for removing leached contaminants. Exercise pens raised carbon dioxide and nitrous oxide emissions but decreased methane emissions. • Non-aerated, aerated pads served as seasonal exercise areas for tie-stall cows. • Efficient woodchip matrix filters pad leachates by removing contaminants. • Aeration failed to enhance leachate contaminant removal in the stand-off pad. • Outside exercise pens reduce greenhouse gas emissions from dairy housing surfaces. [ABSTRACT FROM AUTHOR]

Passive flux samplers (PFSs) packed with adsorbents are used to estimate gaseous emissions. A key condition of their use is maintaining a linear relationship between internal and external air velocities. The performance of PFSs designs depends on the characteristics of the adsorption bed and on the sampler design. The parameters required to enable PFSs to estimate greenhouse (GHG) emissions from agricultural sources were studied. The effect of the particle size of the adsorbent used as collector medium was analyzed theoretically using the Ergun equation. Three orifice plates with 0.5, 0.7 and 1 mm bore diameter were evaluated in order to determine the most appropriate diameter to control air flow through a new passive flux sampler (PFS) prototype while maintaining adequate linearity between internal and external air velocity. The effect of the adsorbent bed thickness (19, 50, 100 and 200 mm) on the internal-external air velocity relationship in the PFS was evaluated. The best performance was obtained using the 0.7 mm orifice plate and an adsorbent bed thickness of 50 mm. Spherical adsorbents with high adsorption capacity are recommended in order to decrease the adsorbent bed thickness and improve sampling performance. A series of experiments showed that the estimated mass flow obtained by the developed PFS was close to the confidence interval of values obtained by direct detection. Thus, the developed PFS can be used as a tool for the estimating of GHG emissions from agricultural sources. [ABSTRACT FROM AUTHOR]

Phosphate rock fertilization is commonly used in peatland restoration to promote the growth of Polytrichum strictum , a nurse plant which aids the establishment of Sphagnum mosses. The present study tested whether 1) phosphorus fertilization facilitates the germination of P. strictum spores and 2) biochar derived from local pig manure can replace imported phosphate rock currently used in peatland restoration. Various doses of biochar were compared to phosphate rock to test its effect directly on P. strictum stem regeneration (in Petri dishes in a growth chamber) and in a simulation of peatland restoration with the moss layer transfer technique (in mesocoms in a greenhouse). Phosphorus fertilization promoted the germination of P. strictum spores as well as vegetative stem development. Biochar can effectively replace phosphate rock in peatland restoration giving a new waste management option for rural regions with phosphorus surpluses. As more available phosphorus was present in biochar, an addition of only 3–9 g m −2 of pig manure biochar is recommended during the peatland restoration process, which is less than the standard dose of phosphate rock (15 g m −2 ). [ABSTRACT FROM AUTHOR]