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The objective of this study was to evaluate the performance of psychrophilic anaerobic digestion in sequencing batch reactors (SBRs) under operating strategies that would optimize process performance and stability while minimizing the interference of the bioreactor operation with regular farm activities. Process performance was evaluated on (i) reduction in pollution potential; (ii) energy recovery; and (iii) odour reduction. Experiments were carried out in twelve 40-L SBRs. Experimental results indicated that psychrophilic anaerobic digestion of swine manure slurry at 20 °C in an intermittently fed SBR (i) reduced the pollution potential of swine manure slurry by removing 84 – 93% of the soluble chemical oxygen demand and 41 – 83% of total chemical oxygen demand; (ii) produced biogas at rates exceeding 0.48 L of CH4 per gram of volatile solids fed; and (iii) successfully reduced odours. Other findings were that (i) for all experimental runs, psychrophilic anaerobic digestion of swine manure slurry in SBRs was very stable; (ii) the process generally performed well without external mixing; and (iii) intermittent feeding of once or three times a week did not affect process stability and performance. As a result, this process requires little energy input and most of the energy produced will be available for farm use. Since this process is very stable, process feeding could be integrated with the routine operation of manure removal from the barn, thereby minimizing interference with other farm operations. Key words: anaerobic, anaerobic treatment, psychrophilic, animal manure, methane production, process control, manure treatment.

Liquid dairy cattle manure was applied at three rates (224, 560 and 879 kg/(ha∙yr) of manure nitrogen (N)) and four different times: in the fall after harvest of silage corn, before seeding, half in the fall and half before seeding, or in winter to continous corn grown on sandy clay loam for 5 yr. Two other plots were included: one received chemical N-P-K fertilizer at recommended rates, and one received neither fertilizer nor manure. Over the 5-yr study, soil organic carbon increased in the surface layer of the high-rate plots, but decreased in the chemically fertilized plot. Soil inorganic N contents measured at harvest in the 0- to 120-cm layer of the manured plots were related to both cumulative and annual N inputs. Bicarbonate extractable phosphorus in the 0- to 15-cm layer increased each year in the medium- and high-rate plots and exceeded 90 μg/g in the high-rate plots after 5 yr. Exchangeable potassium levels increased singificantly in the plow layer of the medium- and high-rate plots. Smaller accumulations occurred in the winter-applied plots than in the fall- and spring-applied plots. Uptake of nutrients by the corn crop increased with manure rate, but generally was not affected by time of application.

The use of conservation tillage is increasing in North America, but information on its effect on water quality in cold climatic regions is limited. To obtain such information, the effect of no-tillage (NT) and conventional tillage (CT) treatments on nitrate-nitrogen (NO3-N) concentration, specific electrical conductivity (EC), and pH in shallow groundwater (1.2, 1.8, 3.0, and 4.6 m depths) was studied over four successive crop years in corn fields (loam soil) of approximately 3 each, located in eastern Ontario. Water table elevation was also monitored during three crop years. Average NO3-N concentration at the 1.2, 1.8, and 4.6 m depths was consistently higher under CT than under NT in every crop year and every season. However, the effect of tillage was not significant at P < 0.05. Nitrate concentration decreased significantly with depth. It was about two to three times the drinking water limit of 10 mg/L as NO~ -N at the 1.2, 1.8, and 3.0 m depths. At the 4.6 m depth, NO~-N concentrations were mostly low but increased with time. Changes in water table elevation appeared to affect NO~-N concentrations at the 1.2 m depth under NT only. At a given depth, EC and pH of groundwater were not affected by tillage treatment. However, within each tillage treatment, values increased significantly with depth. Results from this study indicated a large spatial variability in NO~-N and EC values in groundwater, which could have masked small tillage effects. More intensive temporal and spatial sampling may be required to establish tillage treatment effects, if any.

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