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Abstract Anaerobic digestion of animal by-products was investigated in batch and semi-continuously fed, reactor experiments at 55 °C and for some experiments also at 37 °C. Separate or mixed by-products from pigs were tested. The methane potential measured by batch assays for meat- and bone flour, fat, blood, hair, meat, ribs, raw waste were: 225, 497, 487, 561, 582, 575, 359, 619 dm 3 kg −1 respectively, corresponding to 50–100% of the calculated theoretical methane potential. Dilution of the by-products had a positive effect on the specific methane yield with the highest dilutions giving the best results. High concentrations of long-chain fatty acids and ammonia in the by-products were found to inhibit the biogas process at concentrations higher than 5 g lipids dm −3 and 7 g N dm −3 respectively. Pretreatment (pasteurization: 70 °C, sterilization: 133 °C, and alkali hydrolysis (NaOH) had no effect on achieved methane yields. Mesophilic digestion was more stable than thermophilic digestion, and higher methane yield was noticed at high waste concentrations. The lower yield at thermophilic temperature and high waste concentration was due to ammonia inhibition. Co-digestion of 5% pork by-products mixed with pig manure at 37 °C showed 40% higher methane production compared to digestion of manure alone.

Cassava pulp is a major by-product produced in a cassava starch factory, containing 50–60% of starch (dry basis). Therefore, in this study we are considering its potential as a raw material substrate for the production of methane. To ensure sufficient amounts of nutrients for the anaerobic digestion process, the potential of co-digestion of cassava pulp (CP) with pig manure (PM) was further examined. The effect of the co-substrate mixture ratio was carried out in a semi-continuously fed stirred tank reactor (CSTR) operated under mesophilic condition (37 °C) and at a constant OLR of 3.5 kg VS m−3 d−1 and a HRT of 15 days. The results showed that co-digestion resulted in higher methane production and reduction of volatile solids (VS) but lower buffering capacity. Compared to the digestion of PM alone, the specific methane yield increased 41% higher when co-digested with CP in concentrations up to 60% of the incoming VS. This was probably due to an increase in available easily degradable carbohydrates as the CP ratio in feedstock increased. The highest methane yield and VS removal of 306 mL g−1 VSadded and 61%, respectively, were achieved with good process stability (VFA:Alkalinity ratio < 0.1) when CP accounted for 60% of the feedstock VS. A further increase of CP of the feedstock led to a decrease in methane yield and solid reductions. This appeared to be caused by an extremely high C:N ratio of the feedstock resulting in a deficiency of ammonium nitrogen for microbial growth and buffering capacity.

Biodegradation rates of benzoate and related aromatic compounds, 3-nitrobenzoate, 4-chlorobenzoate, 4-chlorophenol, and 2,4-dichlorophenol by unexposed (unacclimated) and long-term exposed (acclimated) biomass were quantified using a modified fed-batch technique. The acclimated biomass was taken after approximately 1-year of operation from three lab-scale sequencing batch reactors (SBR). These reactors were operated under various cycling electron acceptor conditions with a continuous feed of a synthetic wastewater containing biogenic and nonbiogenic chemicals including benzoate, 3-nitrobenzoate, and 4-chlorophenol, but not 4-chlorobenzoate or 2,4-dichlorophenol. The unexposed biomass was taken from a full-scale wastewater treatment plant, which constituted one of the original sources of inoculum for the lab-scale SBRs. The acclimated biomass manifested high removal rates of benzoate and related aromatic compounds with additional removal of structurally similar chemicals (4-chlorobenzoate and 2,4-dichlorophenol). The unacclimated biomass showed no removal of 3-nitrobenzoate, 4-chlorobenzoate or 2,4-dichlorophenol. Addition of biogenic substrates reduced the degradation of most aromatic compounds tested, but it enhanced 2,4-dichlorophenol removal. Biodegradation rates of each aromatic compound with the biomass from the anoxic/aerobic SBR were further determined under anaerobic (absence of aeration and NO3-), anoxic (no aeration, but with surplus NO3-), standard oxygen (DO > 0.2 mg/L), and elevated oxygen (DO > 25 mg/L) conditions. The removal rate of both benzoate and 3-nitrobenzoate decreased under anaerobic condition but not under the anoxic condition; 4-chlorophenol biodegradation, on the other hand, was reduced significantly under both anoxic and anaerobic conditions. The removal rates of aromatic compounds, particularly those of 3-nitrobenzoate and 2,4-dichlorophenol, increased significantly under elevated dissolved oxygen conditions. Our results demonstrated that when the biochemical conditions shifted from oxygen-respiration to nitrate respiration, to anaerobiosis, the biodegradation rates of test aromatic compounds decreased or ceased.

The Indian Ocean Experiment (INDOEX) was an international, multiplatform field campaign to measure long-range transport of air pollution from South and Southeast Asia toward the Indian Ocean during the dry monsoon season in January to March 1999. Surprisingly high pollution levels were observed over the entire northern Indian Ocean toward the Intertropical Convergence Zone at about 6°S. We show that agricultural burning and especially biofuel use enhance carbon monoxide concentrations. Fossil fuel combustion and biomass burning cause a high aerosol loading. The growing pollution in this region gives rise to extensive air quality degradation with local, regional, and global implications, including a reduction of the oxidizing power of the atmosphere.

Worldwide, 98% of total electricity is currently produced by thermoelectric power and hydropower. Climate change is expected to directly impact electricity supply, in terms of both water availability for hydropower generation and cooling water usage for thermoelectric power. Improved understanding of how climate change may impact the availability and temperature of water resources is therefore of major importance. Here we use a multi-model ensemble to show the potential impacts of climate change on global hydropower and cooling water discharge potential. For the first time, combined projections of streamflow and water temperature were produced with three global hydrological models (GHMs) to account for uncertainties in the structure and parametrization of these GHMs in both water availability and water temperature. The GHMs were forced with bias-corrected output of five general circulation models (GCMs) for both the lowest and highest representative concentration pathways (RCP2.6 and RCP8.5). The ensemble projections of streamflow and water temperature were then used to quantify impacts on gross hydropower potential and cooling water discharge capacity of rivers worldwide. We show that global gross hydropower potential is expected to increase between +2.4% (GCM-GHM ensemble mean for RCP 2.6) and +6.3% (RCP 8.5) for the 2080s compared to 1971–2000. The strongest increases in hydropower potential are expected for Central Africa, India, central Asia and the northern high-latitudes, with 18–33% of the world population living in these areas by the 2080s. Global mean cooling water discharge capacity is projected to decrease by 4.5-15% (2080s). The largest reductions are found for the United States, Europe, eastern Asia, and southern parts of South America, Africa and Australia, where strong water temperature increases are projected combined with reductions in mean annual streamflow. These regions are expected to affect 11–14% (for RCP2.6 and the shared socio-economic pathway (SSP)1, SSP2, SSP4) and 41–51% (RCP8.5–SSP3, SSP5) of the world population by the 2080s.

Aim of the present paper is to investigate and compare the performance of three different possible membrane condenser configurations in terms of amount of recovered liquid water and energy consumption. Membrane condenser is an innovative unit operation utilized for the recovery of evaporated waste water from industrial gases. In the first proposed configuration, the fed waste gas is cooled by cooling water before entering the membrane module; in the second configuration the cooling is obtained inside the membrane module through a cold sweeping gas; the third configuration is in between the two previous ones: the fed waste gas is first partially cooled via an external medium and then a sweeping gas is used for the final cooling of the stream. The achieved results indicate that configuration 2 has the lowest energy consumption, and configuration 3 allows achieving the highest water recovery whereas its energy consumption is in between configuration 1 and 2.

The morphological responses of seedlings of eight African provenances of Vitellaria paradoxa (Shea tree or Karite) to imposed draught stress were compared under nursery experimental conditions. The potted seedlings were subjected to three different watering regimes (87 days after sowing): no water stress (100% of the field capacity, C), moderate water stress (75% of C) and severe water stress (50% of C). Before the application of the stress, we observed genotypical differences in the morphological variables at the scale of leaves and of above-ground parts. The six-month water stress affected aerial growth: all provenances responded to drought by down-regulating growth (in height and in diameter), leaf number and area. Katawki provenance of Uganda performed relatively poorly, possibly of it being a nilotica subspecies, contrary to the others (paradoxa subspecies). There was a lack of correlation between climate of seeds origin, seed characteristics, seeds germination and survival rate of seedlings. The study confirmed the importance of leaf area in the vigor of the initial growth in this species. Thus, Tamale and Karaba provenances performed better than other West African provenances due to their larger leaf area, which was found to be a determining factor of relative growth in height at the seedling stage.

Selection of sheep with low enteric methane (CH4) emissions is a greenhouse gas (GHG) mitigation option suitable for pastoral systems. However, the effect of breeding sheep with low enteric CH4 emissions on excreta output and associated CH4 and nitrous oxide (N2O) emissions and therefore total GHG emissions are not known. The objective of the current experiments were to determine excreta output, and estimate associated GHG emissions, from progeny of low and high enteric CH4 per unit of dry matter intake (DMI) selection line sheep (CH4/DMI). The animals were fed two qualities of cut perennial ryegrass-based pasture (very mature vs. vegetative, 12 animals per CH4/DMI line) in Exp. 1 and cut pasture in two repeated seasons (autumn and winter; 15 animals per CH4/DMI line × 2 seasons) in Exp. 2. Total faecal and urine output was determined on individual animals, followed by enteric CH4 emission measurements in respiration chambers. GHG emissions from urine (N2O) and faeces (CH4 and N2O) were estimated based on New Zealand Agricultural GHG Inventory methodology. There was no interaction between CH4/DMI selection line and diet quality in Exp. 1 or seasons in Exp.2. Total daily faecal output of DM, organic matter (OM) and neutral detergent fibre (NDF; all g/d) and associated calculated faecal CH4 emissions were greater for low compared to high CH4/DMI sheep in Exp. 1 (P 4/DMI selection lines in Exp. 2. Nitrogen (N) excretion and N partitioning into urine, faeces and body retention, and calculated excreta N emissions, were mostly similar between CH4/DMI selection line sheep in both experiments. Except, faecal N output (g/d and per unit of N intake) and associated calculated direct faecal N2O-N emissions (g/d) were greater in low compared to high CH4/DMI sheep in Exp. 1 (P 4 emissions were numerically 8% less (P = 0.15) in Exp.1 and 10% less (P = 0.004) in Exp. 2 and total animal level GHG emissions (CH4 and N2O) were numerically 7% less (P = 0.21) in Exp. 1 and 8% less (P = 0.006) in Exp.2 for progeny of the low compared to the high CH4/DMI line sheep. In conclusion, the magnitude of difference in enteric CH4 (expressed as CO2-equivalent) between low and high CH4/DMI selection line sheep were still present when CH4 from faeces and N2O emissions from urine and faeces were also accounted for. The animal genetic traits were expressed independent of environmental factors, i.e. pasture quality and season.