Animal manure storage facilities are sources of greenhouse gas emissions in Canada, with the majority of emissions in the form of methane and nitrous oxide. This study was conducted to assess how effective adding gypsum powder to cow manure is at reducing the emissions of methane and nitrous oxide. At a pilot-scale research facility in Nova Scotia, Canada, gypsum powder was added to tanks containing ∼10,000 L of local dairy manure in duplicate at three rates: low rate (3.2 g L-1), high rate (7.1 g L-1), and the control (0 g L-1). Each manure tank was enclosed within a steady-state chamber, and gas samples were manually taken using a syringe from the exhaust into pre-evacuated vials at regular intervals between June and November (143 days). Using gas chromatography, methane and nitrous oxide measurements were analyzed from each vial, allowing for calculations of cumulative emissions and CO2-e. Compared to the control, both the high rate and low rate of gypsum significantly reduced cumulative methane emissions. Though the cumulative nitrous oxide emissions were reduced using both rates of gypsum, the nitrous oxide emissions were minor and not statistically significant. Methane emissions were reduced by 87% using the low rate of gypsum and by 92% using the high rates of gypsum. Gypsum additive to slurry in storage facilities is a safe and effective mitigation strategy to reduce greenhouse gas emissions. Further research is required to support on-farm application rates and feasibility.

Water use is an important environmental concern for the dairy sector. There are two kinds of water use in the dairy sector, direct and indirect. Electricity generation (e.g., cooling water, evaporation, etc.) is an indirect use of water and a significant contributor to the overall water budget depending on how electricity is generated. In Canada, the dairy industry is distributed across 10 provinces each with a wide range of electricity generation sources in their grid mix, making it an interesting case study. For a dairy farm that uses 1021 kWh cow-1 y-1 (9.4 – 10.6 kWh per 100 kg milk, depending on the province), the average water use related to generating electricity was estimated to be 3.48 L kg-1 milk (range: 1.40 – 5.77 L kg-1, depending on the electricity grid). Energy conservation technologies could reduce electricity use by as much as 30 % and thus reduce water use by 1.04 L kg-1 milk on average (range: 0.42 – 1.73 L kg-1). Installing an on-farm solar array (0.40 kWp cow-1; i.e. one 400-watt solar panel per cow) could lower grid-electricity-related water use by 35 – 51 % (or by 0.57 – 2.71 L kg-1). Solar array sized with the capacity to reach net-zero electricity is feasible and can eliminate grid-electricity-related water use. This study highlights that dairy farms can achieve substantial water savings by strategically using electricity conservation and renewables, with the magnitude depending on the electricity grid mix, a relationship that has yet to be analyzed in current literature.

An increasing proportion of dairy farms are adopting automated milking systems (AMS). At the same time, the dairy industry is actively exploring strategies to reduce the water footprint of milk production. Automated milking systems have different cleaning procedures than traditional conventional milking systems (CMS), so the effect on water use is a potentially important consideration. Previous studies of AMS approximately a decade ago showed ∼50% more direct water use compared with CMS; however, those studies were based on older technology and compared different farms. The current study measured whole-farm water use partitioned into drinking (for consumption) and service water (for cleaning) on a dairy farm in Eastern Canada. The dairy farm milked 110 to 120 cows initially using CMS and then changing to AMS. Results showed that the pattern of water use changed with the AMS to increased peak drinking water and decreased peak service water use. Cows produced more milk and consumed more water with the AMS. Overall service water use per cow decreased from 30.9 ± 7.7 L·d-1 with the CMS to 22.5 ± 4.0 L·d-1 with the AMS, and overall service water use per unit of milk decreased from 0.98 ± 0.25 L·L-1 with the CMS to 0.68 ± 0.13 L·L-1 with the AMS. Daily service water use was also more consistent with the AMS (CV = 17.9%) versus the CMS (CV = 24.8%). With the AMS, the farm used significantly more water, produced significantly more milk, and achieved significantly better water use efficiency per liter of milk.

Reducing methane (CH4) emissions from dairy farms is a key objective in limiting total greenhouse gas emissions from the livestock industry. Reducing CH4 emissions from manure storage using additives may provide an achievable near-term contribution to this long-term goal in alignment with the International Dairy Federation's initiative on pathways to net zero. Sulfate-based H2SO4 and the sulfate-containing nonacid CaSO4 have effectively suppressed methane emissions in lab studies at a single temperature. The present study analyzes the effect of temperature on the efficacy of these two additives, bridging the gap between common laboratory conditions and average on-farm temperature. We found superior cumulative suppression, higher peak suppression, and longer duration of high-end suppression at lower temperatures when comparing controls to additive experiments at 24, 21, and 18 degrees C over 120 days. Peak mitigation increased as temperature decreased, culminating at 82.9% and 57.6% for H2SO4 and CaSO4, respectively, at 18 degrees C. Additives remained effective for longer at lower temperatures, with H2SO4 maintaining >= 70% peak mitigation (PM) for 102 days at 18 degrees C, but only 48 days at 24 degrees C; CaSO4 retained >= 70% PM for 87 days at 18 degrees C, but only 38 days at 24 degrees C. PM for each additive occurs at similar thermal times, despite appearing different at conventional times. Our analysis creates a link between the efficacy of CH4 mitigation and local temperatures, which can be related to cumulative heat (thermal time/degree-days) to establish site-specific guidance for CH4 mitigation protocols.

Dairy farmers are interested in reducing the carbon footprint of milk. Reducing methane (CH 4 ) emissions is a key part of this goal, and manure is a significant CH 4 source. Technologies like anaerobic digesters for biogas production are effective; however, adoption rates are slowed by upfront costs and infrastructure needs. Achieving near-term emission reductions needs low-cost alternatives that can be quickly and widely adopted. Previous studies have shown that “acidification” of manure by adding sulfuric acid (H 2 SO 4 ) suppressed CH 4 emissions; however, widespread adoption may be hindered by the challenge of handling acid on farms. This laboratory study was performed for 157 days at 24°C, and compared the efficacy of a sulfate-based non-acidic fertilizer (CaSO 4 ), and two rates of acidification, one at pH > 7 and one at pH < 7, for a sulfate-based acid (H 2 SO 4 ) and a sulfate-free acid (H 3 PO 4 ). Methane suppression by CaSO 4 at multiple rates was also analyzed. Two mechanisms of suppression were observed: acidification had a demonstrable early effect, lowering cumulative CH 4 emission within 40 days by up to 65% for H 2 SO 4 and 54% for H 3 PO 4 , while sulfate-containing compounds showed increasing suppression after 50 days. Final cumulative CH 4 suppression was up to 63% for CaSO 4 and 91% for H 2 SO 4 , while H 3 PO 4 was least effective. These results suggest H 2 SO 4 is highly effective due to the combination of acidity and sulfate. Adding sulfate alone (CaSO 4 ) was more effective than adding acid alone (H 3 PO 4 ). Hence, sulfate-based additives—like gypsum—may hold promise as an alternative near-term solution for dairy farms to make large CH 4 reductions.

In-service inspection is a critical element in confirming the integrity of permanent floating production unit mooring systems. Over the unit's operating life, which will typically span 20 years or more, these inspections provide the majority of the condition information on the mooring components and overall system. This information enables operators to proactively address mooring issues caused by degradation mechanisms or deviations in mooring line tensions that could reduce the system capacity and potentially result in premature failure. However, detailed guidance on inspection intervals, and in particular inspection scope, is limited for permanent mooring systems. To address this identified industry need, the DeepStar® technology consortium initiated Project 19403, "Improving Mooring Integrity through Standardized Inspection and Fit-For-Service Assessment" to develop best inspection practice guidance for permanent mooring systems [1]. This paper describes the content and benefits of this new mooring inspection guidance document developed as part of the DeepStar® 19403 project [1] with the support of subject matter experts from major operator companies, Class societies and mooring consultancies. The paper will describe how this new guidance compliments and expands current industry Recommended Practice (RP) guidance. Key aspects related to in-service survey intervals, component inspection work scopes and inspection methods will be discussed as well as the execution planning of in-service mooring inspections. To facilitate inspection work, the predominate deterioration mechanisms are introduced which are corrosion, wear and fatigue. Other types of deteriorations are also summarized. Default in-service survey intervals (frequencies) and component inspections are recommended. In-service inspection methods are reviewed, from General Visual Inspection (GVI) and Close Visual Inspection (CVI) to advanced Non-Destructive Testing (NDT). Guidance on assessing the residual capacity of a damaged or flawed mooring component, known as fitness-for-service, is also covered within the new mooring inspection guidance.

Addition of sulfuric acid (H 2 SO 4 ) to liquid dairy manure (slurry) reduces methane (CH 4 ), nitrous oxide (N 2 O), and ammonia (NH 3 ) emissions. There is interest in understanding how gaseous emissions respond to decreasing rates of acidification, to determine economically optimum application rates. Acidification rates were tested ranging from 0 to 2 g sulfuric acid (H 2 SO 4 ) L −1 slurry in six meso-scale outdoor storage tanks, each filled with 10.6 m 3 slurry and stored for 114 d. Results showed that the rate of acidification for maximum inhibition of CH 4 and NH 3 emissions varied markedly, whereas N 2 O reductions were modest. Reductions of CH 4 increased with acid rate from 0 to 1.2 g L −1 , with no additional response beyond >1.2 g L −1 . In contrast to CH 4 , inhibitions of NH 3 showed a linear response across all rates, although reductions were ≤ 30%. Thus, higher acidification rates would be required to achieve greater NH 3 emission reductions. Our findings indicate that achieving >85% NH 3 emissions reductions would require 4 × more acid than achieving >85% CH 4 reductions. Decisions on optimum H 2 SO 4 rates will depend on the need to mitigate CH 4 emissions (the primary greenhouse gas emitted from stored liquid manure) or reduce NH 3 emissions (which is regulated in some regions). These results will help develop guidelines related to the potential costs and benefits of reducing emissions through acidification.

The blue water footprint (WF) is an indicator of freshwater required to produce a given end product. Determining the blue WF for milk production, the seasonal water use and the impact of water conservation are important sustainability considerations for the dairy industry in Ontario (Canada). In this study, a water footprint network (WFN) method was used to calculate the seasonal blue WF’s from in-barn water use data and the fat–protein-corrected milk (FPCM) production. Various water conservation options were estimated using the AgriSuite software. Results showed that the total water use (L of water·cow−1·d−1) and the average blue WF (L of water·kg−1 of FPCM) were 246.3 ± 6.8 L·cow−1·d−1 and 7.4 ± 0.2 L·kg−1, respectively. The total water use and the blue WF could be reduced to 182.7 ± 5.1 L·cow−1·d−1 (25.8% reduction) and 5.8 ± 0.1 L·kg−1 (21.6% reduction), respectively, through adaptive water conservation measures as the reuse of the plate cooler and milk house water. For example, conservation practices could reduce the milk house wash water use from 74.3 ± 8.8 L·cow−1·d−1 to 16.6 ± 0.1 L·cow−1·d−1 (77.7% overall reduction).

Although much of the manure in Canada is surface-applied to forages, little research exists evaluating time of year (Time) and rate (Rate) of application on forage yield and nutrient uptake. Field trials (10 yr) on two soils (sandy loam upland and silty clay loam dykeland) investigated this. Experimental arrangement was a factorial [Time (spring, summer, early, and late fall manure applications)] plus a control [spring-applied ammonium nitrate fertilizer (ANF)] in a Latinized split plot. ANF at 0, 25, 50, 100 and 200 kg N·ha−1; 0, 75, 150, and 300 as semi-solid beef (SSM) and 150 kg N·ha−1 as liquid dairy manure (LDM), constituted respective splits. The Time × Rate interaction, later in the trial on the upland soil, showed higher yields and nutrient uptakes with fall manure application. There was little interaction on the dykeland soil; summer application resulted in higher yields at times. For both soils, the optimal long-term application rate of SSM was approximately 150 kg N·ha−1 while that of ANF was approximately 100 kg N·ha−1. Inherent fertility of dykelands resulted in lesser responses to manure addition. Negligible and significant residual N occurred with fertilizer and manure, respectively. Nitrogen, phosphorus, potassium, calcium, magnesium, manganese, copper, zinc, and boron uptakes were due to amendment impact on yield. The recommended rate is 150 kg N·ha−1 of SSM or LDM applied in fall and summer to Maritime grasslands grown on upland and dykeland soils, respectively. Yield differences may not warrant producers adjusting timing of in-season manure application.

Highlights Studies of electricity use were reviewed, representing five continents. Considering all farm types, electricity use averaged 7.7 kWh 100 kg -1 milk and 612 kWh cow -1 y -1 . Pasture-based dairy systems used less electricity than barn-based systems (475 vs. 769 kWh cow -1 y -1 ). By combining several conservation technologies there is potential to reduce electricity demand by one-third. Dairy farms can reach net zero electricity by combining renewable energy production with conservation. Abstract. This review summarizes electricity use on dairy farms, with a focus on how energy is used, energy use indices (EUI), conservation strategies, and generation of renewable energy to reach net zero. EUI of electricity consumption varied between the identified studies primarily based on farm management system (confined, pasture-based), housing type (tie-stall, free-stall), and region (North America, Europe, Asia, Africa, Oceania). The highest electricity usage was associated with milking and milk cooling systems, which, on average, accounted for 23% and 22% of total electricity use, respectively. Energy use scaled per cow (EUI c ) was lower, on average, for pasture-based dairy systems than for confined systems (475 vs. 769 kWh cow -1 y -1 ). Considering milk production, the average EUI scaled to milk (EUI m ) was lower for pasture-based systems (6.6 kWh 100 kg -1 ) than for confined systems 9.2 kWh 100 kg -1 . Considering all non-irrigated farm types, EUI m averaged 7.7 kWh 100 kg -1 and EUI c averaged 612 kWh cow -1 y -1 . There was a large range of EUI, with higher values associated with automated milking systems and irrigation. Electricity consumption by the global dairy sector (excluding irrigation) was estimated using the average EUI m at approximately 64.2 TWh y -1 . The main conservation technologies include variable speed drives (milk vacuum pumps, milking systems, fans), pre-cool heat exchangers, refrigeration heat recovery systems, energy-efficient light fixtures (compact fluorescents, light emitting diodes), and efficient ventilation (high-volume low-speed fans). Theoretical savings of up to 32% overall could be achieved by combining several technologies. Feedback from electricity monitoring can inform dairy farmers of their energy use pattern to guide decisions to reduce consumption. Tools for predicting energy use and related costs on dairy farms, which can indicate potential energy savings from operational changes, were reviewed. By combining conservation methods with renewable energy from biogas or solar, many dairy farms can produce enough electricity to reach net zero electricity. For example, a hypothetical barn-based 250 milking-cow dairy farm consumed 1021 kWh cow -1 y -1 , on average, and could produce approximately 1095 kWh cow -1 y -1 using a biodigester or 960 kWh cow -1 y -1 using rooftop photovoltaic solar panels. Keywords: Conservation, Dairy footprint, Electricity use, Electricity partitioning, Energy utilization index, Renewable energy.

HighlightsEvaporation from clear water, manure, and separated liquid manure was 4.6 mm d-1 on average.Straw, foam, geotextile, and roof covers decreased evaporation by 54%, 53%, 31%, and 21%, respectively.Albedo was highest for floating foam covers and lowest for metal roof covers.Straw, foam, and geotextile increased manure temperature compared to uncovered manure. ABSTRACT. Evaporation is a key component of the surface energy budget of liquid manure. Models rely on accurate energy budgets to predict manure temperature, which in turn is used to model temperature-dependent greenhouse gas emissions from liquid manure storages. Due to lack of data, it has been assumed that liquid manure has similar evaporative properties to water; however, this assumption may be inaccurate. Many factors, including manure crusting, covers, and turbidity, are all likely to affect the surface energy budget and the evaporation rate. This experiment investigated the differences in evaporation between eight treatments, including water, dyed water, raw and separated liquid manure, and four commonly used covers (straw, geotextile, foam, and roof), by measuring weekly evaporation. Albedo, surface temperatures, and internal temperatures were also measured to determine treatment effects. Over the 10-week study, no significant difference was found between the evaporation rates of water, raw manure, and separated liquid manure, with an average rate of 4.6 mm d-1. Notably, the raw manure did not form a consistent surface crust, which may explain the similarities in evaporation rates in this study and is unlikely to represent manure with a crust. Overall, covers significantly decreased evaporative losses by between 21% and 54% compared to uncovered raw manure. Average evaporation rates of the covered treatments were 1.9 mm d-1 for straw cover, 2.0 mm d-1 for foam cover, 2.9 mm d-1 for geotextile cover, and 3.4 mm d-1 under a roof cover. Similarities between each treatment and water as well as between the four covered treatments and the uncovered raw manure were found using linear regression on weekly evaporation. Generally, the uncovered treatments were more similar and could be predicted (high R2) by multiple linear regression with environmental variables, while the covered treatments differed more and were not as well predicted (lower R2). Results from this study can help adjust evaporation rates in biophysical models to improve estimates of manure temperature, tank holding capacity, and emission predictions. Keywords: Evaporation, Dairy manure, Liquid manure, Manure covers, Manure management.

Greenhouse gas (GHG) emissions, especially methane (CH4 ), from manure storage facilities can be substantial. Methane production requires adapted microbial communities ("inoculum") to be present in the manure. Complete removal of liquid dairy manure (thus removing all inoculum) from storage tanks in the spring has been shown to significantly reduce CH4 emissions over the following warm season. This study examined whether the same mitigation effect would occur after fall removal of liquid dairy manure. Emissions of CH4 , nitrous oxide (N2 O), ammonia (NH3 ), and CO2 were measured from six 11.88-m3 tanks equipped with flow-through chambers. There were three inoculated controls (20% inoculum) and three uninoculated treatments, where inoculum was completely removed in the fall/winter (0% inoculum). Direct N2 O and NH3 (indirect N2 O) were minor contributors to the total GHG budget, contributing <2% on a CO2 equivalent (CO2 e) basis. Removal of inoculum led to a 34% decrease in total emissions on a CO2 e basis and to a 29% decrease in the CH4 conversion factor compared with the inoculated control (0.37 vs. 0.52; p = .01). Overall, removing inoculum in the fall reduced CH4 emissions from manure storage tanks; however, fall inoculum removal was less effective than in a previous study where inoculum was removed in the spring. The timing of inoculum removal may affect the efficiency of this CH4 mitigation strategy. However, this method may be impractical for larger manure storage tanks. Further study is required to overcome challenges of time-sensitive, complete inoculum removal from farm-scale storage tanks.

ABSTRACT Acidification with sulphuric acid and cleaning residual manure in tanks are promising practices for reducing methane (CH4), which is a potent greenhouse gas. To date, no data are available on CH4 reductions from acidifying only residual manure (rather than all manure). Moreover, long-term effects of manure acidification (i.e. inoculating ability of previously acidified residual manure in the subsequent storages) are not known. To address these gaps, fresh manure (FM; 150 mL) combined with treated or untreated inoculum (30 mL) were anaerobically incubated at 17°C, 20°C, and 23°C for 116 d. Acidified treatments, regardless of location of acid addition, reduced CH4 production by 81% at 17°C, 78% at 20°C, and 19% at 23°C compared to the control (untreated FM and untreated inoculum). To test long-term acidification effects, FM was inoculated with manure that had been acidified 6-months prior. This created comparable CH4 production to FM with no inoculum and reduced CH4 production by 99% at 17°C and 20°C, and 49% at 23°C compared to the control. Results indicate that residual slurries of acidified manure become poor inoculants in subsequent storage, hence manure acidification has a long-term treatment effect in reducing CH4 production. This could reduce how often acidification is needed in dairy manure tanks and also increasing its cost-effectiveness for farmers. GRAPHICAL ABSTRACT

Liquid manure storages are an important source of greenhouse gases (GHG) on dairy farms. Methane (CH4) and nitrous oxide (N2O) are the predominant GHGs, while ammonia (NH3) is an indirect source of N2O. Addition of acid to manure has shown promising emission reductions, however, cost of acidification may be unfeasible for farmers. Fully cleaning storages has also shown to reduce CH4, due to removal of inoculating effects of residual manure (“inoculum”) on fresh manure (FM). However, complete removal of inoculum is practically impossible on large farms, thus acidifying only the inoculum may reduce GHGs without requiring acidification of all FM. This study aimed to quantify the effect of acidified inoculum on CH4, N2O, and NH3 emissions from stored manure and quantify the changes in methanogen abundance and activity. Emissions were measured from six 10.6 m3 storages filled with 20% inoculum (1-year-old manure) and 80% FM. Inoculum was treated in three ways: untreated (control); previously acidified (1-year prior); and newly acidified with 70% H2SO4 (1.1 L m−3 manure). The CH4 and N2O emissions were continuously measured from June—November using tunable diode trace gas analyzers coupled with venturi air flow systems. The NH3 emissions were measured at 24-h intervals 3 × weekly using acid traps. The activity and abundance of methanogens were quantified by targeting the Methyl Coenzyme M Reductase A (mcrA) gene and transcript which encodes a subunit of the key enzyme that catalyzes the final step of methanogenesis. Bacterial abundance was quantified by targeting the bacterial 16S rRNA gene. Quantifications were performed using quantitative real-time PCR. CH4 emissions were reduced by 77% using newly acidified inoculum and 38% using previously acidified inoculum, compared to the control with untreated inoculum (36.1 g CH4 m−2). Significant treatment reductions in mcrA gene and transcript abundance suggest that CH4 reductions were caused by disruption of methanogen activity. NH3 and N2O emissions were reduced by 33 and 73% using acidified inoculum and 23 and 50% using previously acidified inoculum, respectively, compared to the control. Results suggest that lower acid rates and acidifying less frequently may still have good treatment effects while minimizing cost.

In Kuwait, dairy farming faces challenges due to its significant water demands. The current study assessed seasonal patterns of water use to estimate the blue water footprint (WF) and grey WF per kg of fat protein corrected milk (FPCM) for confined dairy farming systems in Kuwait. Blue and grey WFs were evaluated using data from three operational farms. The average blue WF (L·kg-1 FPCM) was estimated to be 54.5 ± 4.0 L·kg-1 in summer and 19.2 ± 0.8 L·kg-1 in winter. The average grey WF (generated from milk house wastewater) was assessed on bimonthly basis and determined based on its phosphate (PO4) concentration (82.2 ± 14.3 mg·L-1) which is the most limiting factor to be 23.0 ± 9.0 L·kg-1 FPCM d-1. The outcomes indicate that enhancing the performance of dairy cows and adopting alternative water management strategies can play a role in minimizing the impacts of confined dairy farming systems in Kuwait on water quality and quantity.

This study explores the variation of liquidmanure temperature (T-m) and CH4 emissions associated with contrasting regional climates, inter-annual weather variation, and manure storage emptying. As a case-study, six regions across Canada were used, spanning 11 degrees 32' latitude and 58 degrees 30' longitude. Annual average air temperatures ranged from 3.9 degrees C (prairie climate) to 10.5 degrees C (maritime climate), with an overall average of 6.6 degrees C. A model predicted Tm over 30 years, using daily weather (1971-2000), and over one "normal" year (30-year average weather). Modelled T-m was then used in Manure-DNDC to model daily CH4 emissions. Twomanure storage emptying scenarios were simulated: (i) early spring and autumn, or (ii) late spring and autumn. Regional differences were evident as average Tm ranged from 8.9 degrees C to 14.6 degrees C across the six locations. Early removal of storedmanure led to warmer Tm in all regions, and the most warming occurred in colder regions. Regional climate had a large effect on CH4 emissions (e.g. 1.8x greater in the pacificmaritime and great lakes regions than the prairie region). Inter-annual weather variability led to substantial variation in inter-annual CH4 emissions, with coefficient of variation being as high as 20%. The large inter-annual range suggests that field measurements of CH4 emissions need to compare the weather during measurements to historical normals. Early manure storage emptying reduced CH4 emissions (vs late removal) in some regions but had little effect or the opposite effect in other regions. Overall, the results from this modelling study suggest: i) Tm differs substantially from air temperature at all locations, ii) accurate estimates of manure storage CH4 emissions require region-specific calculations using T-m (e.g. in emission inventories), iii) field measurements of CH4 emissions need to consider weather conditions relative to climate normal, and iv) emission mitigation practices will require region-specific measurements to determine impacts. Crown Copyright (C) 2020 Published by Elsevier B.V. All rights reserved.

Liquid manure storages are a significant source of methane (CH4) emissions. Farmers commonly agitate (stir) liquid manure prior to field application to homogenize nutrients and solids. During agitation, manure undergoes mechanical stress and is exposed to the air, disrupting anaerobic conditions. This on-farm study aimed to better understand the effects of agitation on CH4 emissions, and explore the potential for intentional agitation (three times) to disrupt the exponential increase of CH4 emissions in spring and summer. Results showed that agitation substantially increased manure temperature in the study year compared to the previous year, particularly at upper- and mid-depths of the stored manure. The temporal pattern of CH4 emissions was altered by reduced emissions over the subsequent week, followed by an increase during the second week. Microbial analysis indicated that the activity of archaea and methanogens increased after each agitation event, but there was little change in the populations of methanogens, archaea, and bacteria. Overall, CH4 emissions were higher than any of the previous three years, likely due to warmer manure temperatures that were higher than the previous years (despite similar air temperatures). Therefore, intermittent manure agitation with the frequency, duration, and intensity used in this study is not recommended as a CH4 emission mitigation practice. Implications: The potential to mitigate methane emissions from liquid manure storages by strategically timed agitation was evaluated in a detailed farm-scale study. Agitation was conducted with readily-available farm equipment, and targeted at the early summer to disrupt methanogenic communities when CH4 emissions increase exponentially. Methane emissions were reduced for about one week after agitation. However, agitation led to increased manure temperature, and was associated with increased activity of methanogens. Overall, agitation was associated with similar or higher methane emissions. Therefore, agitation is not recommended as a mitigation strategy.

Liquid dairy manure storages emit large amounts of methane (CH4), nitrous oxide (N2O) and ammonia (NH3). Gradually filling manure storages is a standard practice, however, most studies have batch filling approaches. Gradual manure filling may emit different GHGs when inoculum is present, as it changes the substrate/microorganism ratio, manure temperature, and distribution of solids. This study compared CH4, N2O and NH3 emissions from gradually-filled and batch-filled 11.9 m3 capacity liquid dairy manure tanks with 0%, 10% or 20% inoculum over 122 day of storage. On average, gradually-filled tanks had 1.8 °C higher manure temperature, which may have contributed to a 12% increase in total CH4 emissions to 6.26 kg m−3 and 28% increase in total NH3 emissions to 328 g m−3. The absence of inoculum reduced CH4 emissions by 25% and 23% compared to the 10% inoculum tanks (6.48 kg m−3) and 20% inoculum tanks (6.31 kg m−3), respectively. Absence of inoculum had no effect on N2O and NH3 emissions. Gradual filling of tanks containing inoculum increased CH4 emissions by 27% to 7.38 kg m−3, while in the absence of inoculum CH4 emissions were reduced by 29% to 4.03 kg m−3. Our results suggest that research using inoculant in batch-filled manure storage systems may underestimate GHG emissions. Future research should further characterize the effects of gradual filling on solids and temperature profiles, and substrate availability linked to production of GHGs.

Hydrogen peroxide (H 2 O 2 ) is an oxidizing agent used to disinfect recirculated irrigation water during the production of organic crops under controlled environmental systems (e.g., greenhouses). To characterize the phytotoxic effects and define a concentration threshold for H 2 O 2 , three microgreen species [arugula ( Brassica eruca ssp. sativa ), radish ( Raphanus sativus ), and sunflower ( Helianthus annuus ‘ Black Oil’)], and three lettuce ( Lactuca sativa ) cultivars, Othilie, Xandra, and Rouxai, were foliar sprayed once daily with water containing 0, 25, 50, 75, 100, 125, 150, or 200 mg·L −1 of H 2 O 2 from seed to harvest under greenhouse conditions. Leaf damage was assessed at harvest using two distinct methods: 1) the percentage of damaged leaves per tray and 2) a damage index (DI). Applied H 2 O 2 concentrations, starting from 25 mg·L −1 , increased the percentage of damaged leaves in every species except ‘Black Oil’ sunflower, which remained unaffected by any applied concentration. Symptoms of leaf damage manifested in similar patterns on the surface of microgreen cotyledons and lettuce leaves, while mean DI values and extent of damage were unique to each crop. Fresh weight, dry weight, and leaf area of all crops were not significantly affected by daily H 2 O 2 spray. Identifying how foliar H 2 O 2 damage manifests throughout the crop, as well at individual cotyledon or leaf surfaces, is necessary to establish an upper concentration threshold for H 2 O 2 use. On the basis of the aforementioned metrics, maximum recommended concentrations were 150 mg·L −1 (radish), 100 mg·L −1 (arugula) for microgreens and 125 mg·L −1 (‘Othilie’), 75 mg·L −1 (‘Rouxai’), and 125 mg·L −1 (‘Xandra’) lettuce.