Théophile Paré

Transformations of carbon and nitrogen during composting of animal manure and shredded paper

Abstract Composts produced from animal manures and shredded paper were characterized in terms of their carbon (C) and nitrogen (N) forms and C mineralization. Total, water-soluble, acid-hydrolyzable and non-hydrolyzable C and N contents were determined on composts sampled on days 0, 11, 18, 26, 33, 40 and 59 after composting was initiated. Water-soluble and acid-hydrolyzable C and N decreased during composting, whereas non-hydrolyzable C remained relatively constant, and non-hydrolyzable N greatly increased during composting. The water-soluble forms of N were characterized by a decrease of ammomium (NH4+-N) at the beginning of composting, followed by an increase of nitrate (NO3–-N) towards the end of composting. The mineralization of C in composted materials was generally higher at the beginning than at the end of composting, whereas no differences were observed for mineralization of C in non-hydrolyzable materials. The addition of N inhibited C mineralization in composts except in samples collected on days 40 and 59, while C mineralization was strongly stimulated by adding N to the non-hydrolyzable materials. The data suggest that the N forms in the non-hydrolyzable materials were chemically similar and not readily available to microbes, indicating that the C/N ratios often used to assess the biodegradability of organic matter and to develop compost formulations should be based on biologically available N and C and not on total N and C.

Extractability of trace metals during co-composting of biosolids and municipal solid wastes

Abstract Composts made from biosolids and municipal solid wastes contain heavy metals which may be exported outside soil systems by plants, animals and surface and subsurface waters after the compost has been added to soils. Chemical distributions of Cu, Zn, Cr, Pb, Ni and Co were determined by eight sequential extractions of co-composted materials sampled on days 0, 13, 27 and 41. The concentrations of residual Zn, Cr, Cu and Pb increased by 145, 124, 73.6 and 26.3% during the composting period, respectively, whereas the concentration of residual Ni remained relatively constant and that of Co decreased by 60% over the same period. These results show that co-composting contaminated residues substantially reduces the extractability and exchangeability of four out of six heavy metals, suggesting that the risks of entering the food chain and contaminating crops, animals and water reserves would be equally reduced. Fourier-transform infrared spectra showed that heavy metals in the compost are bonded to COO- groups of the organic matter.

Chemical changes during composting of a paper mill sludge–hardwood sawdust mixture

Abstract Recycling of paper mill sludge (PMS) by composting is becoming an acceptable practice for converting these chemically complex materials into useful soil amendments, while eliminating negative environmental impacts. The organic composition of a PMS–hardwood sawdust mixture was investigated during composting to better understand the changes in main chemical components. Pyrolysis-field ionization mass spectrometry (Py-FIMS) and cross polarization-magic angle spinning 13C nuclear magnetic resonance (CP-MAS 13C NMR) were employed to characterize the organic composition of the PMS composted materials. The spectroscopic data revealed that the major components of the PMS were lipids, sterols, lignin, N-compounds, and carbohydrates. By the end of composting (at biomaturity), concentrations of carbohydrates and lignin became more prominent, while those of lipids, sterols and proteinaceous components decreased. Increases in carbohydrates and decreases in paraffinic C, proteinaceous C and C in OCH3 groups appeared to be related to increased microbial activity. Other chemical changes observed during composting were increases in aromatic C, phenolic C, and in aromaticity. While the total C and N contents decreased by about only 12.0%, the compost lost 50% of its initial weight. At biomaturity, the compost consisted primarily of polysaccharide/carbohydrate materials, specifically cellulose and acidic polysaccharides (uronic acids) in combination with smaller quantities of lignin.

Organic matter quality and structural stability of a Black Chernozemic soil under different manure and tillage practices

Abstract No-tillage (NT) and addition of organic matter can improve soil aggregation and affect soil organic matter (SOM) levels. The effects of short-term (3 years, 1993–1996) conventional tillage (CT), NT, and cattle manure applications on SOM quality and water-stable aggregates (WSA) were investigated on a Melfort silty clay loam (Orthic Black Chernozem) at Melfort (Saskatchewan, Canada). Four methods for managing manure (dry weight basis) within CT and NT were established: fresh manure (FM) was applied at the beginning of the experiment at 23.0 Mg ha−1 and annually at 4.5 Mg ha−1, whereas stockpiled manure (SM) with equal N concentration to FM was applied at the beginning of the study at 23.0 Mg ha−1 and annually at 4.5 Mg ha−1. The control treatment consisted in annual application of 81.0 kg N ha−1 as ammonium nitrate and 9.3 kg P ha−1 as monoammonium phosphate, according to soil test recommendations. Soil samples (0–15 cm) were collected at the end of the 3-year period and lipids were extracted with diethyl ether (DEE) and chloroform (CHCl3) to assess SOM quality. Water-stable aggregates were measured with and without ethanol pretreatment and before and after extraction of unbound lipids. The amounts of C and N was not affected by the treatments. Between NT and CT, the changes in SOM were expressed by an increase of 21% of the amounts of total extractable lipids (TEL) in the CT soils, whereas in the NT soils, the DEE/CHCl3 ratio used to assess the degree of biodegradability of OM increased by 40%. Following the application of FM, the stability of soil aggregates against the dissolution and dispersive actions of water decreased by 13 and 16% in CT and NT soils, respectively; however, this effect was compensated by an equivalent increase in resistance to slaking forces. In contrast, the incorporation of SM did not affect the stability of soil aggregates against the dissolution and dispersive actions of water, but increased by 7% the resistance of aggregates to slaking forces.

Extractable Soil Lipids and Microbial Activity as Affected by Bt and Non Bt Maize Grown on a Silty Clay Loam Soil

Pyrolysis‐gas (Py‐GC) chromatography was used to characterize extractable lipids from Bt and non‐Bt maize shoots and soils collected at time of harvesting. Py‐GC‐MS (mass spectrometry) showed that the concentrations of total alkenes identified in non‐Bt shoots and soils were 47.9 and 21.3% higher than in Bt maize shoots and soils, respectively. N‐alkanes identified were of similar orders of magnitude in Bt and non‐Bt maize shoots, but were 28.6% higher in Bt than in non‐Bt soils. Bt maize shoots contained 29.7% more n‐fatty acids than non‐Bt maize shoots, whereas the concentrations of n‐fatty acids in Bt soils were twice as high as those in non‐Bt soils. Concentrations of unsaturated fatty acids in Bt maize shoots were 22.1% higher than those in non‐Bt maize shoots, while concentrations of unsaturated fatty acids were 22.5% higher in non‐Bt than in Bt soils. The cumulative CO2–C evolved from soils under Bt and non‐Bt crops was 30.5% lower under Bt as compared to non‐Bt crops, whereas when maize shoots were added to Bt and non‐Bt soils, the decrease in CO2–C evolved were 16.5 and 23.6%, respectively. Our data showed that the cultivation of Bt maize significantly increased the saturated to unsaturated lipid ratios in soils which appeared to negatively affect microbial activity.

Growth substrates made from duck excreta enriched wood shavings and source-separated municipal solid waste compost and separates: physical and chemical characteristics.

Production and use of compost is an effective means to reduce wastes, and offers a large potential as growth substrates and source of nutrients. The objective of this study was to determine the physical and chemical characteristics of duck excreta enriched wood shavings (DMC) and source-separated municipal solid waste (MSW) composts and separates, and to assess the physical characteristics of growth substrates made from these two composts and selected substrates. MSW compost separates were the following sizes: F1 > 4 mm diameter, 2 mm < F2 < 4 mm, 1 mm < F3 < 2 mm and F4 < 1 mm. Growth substrates were prepared by mixing DMC and F2 and F3 MSW separates (M/M ratios). Growth substrates A-E consisted exclusively of 10-60% DMC and 20-60% of MSW separates F2 and F3. Growth substrates F-J, and K-O were the same as substrates A E, with 15% M/M brick fragments or shredded plastic added as porosity agents, respectively. Growth substrates (BE/S) made of black earth (BE) and sandy loam soil (Ls) in a 1:4 (M/M) ratio, commercially available peat substrate (Pr) and an in-house sphagnum peat-based substrate (Gs) were used for comparison. Principal component analysis (PCA) showed that DMC was a better material than MSW with respect to porosity and water field capacity. MSW compost and separates differed by their relatively high levels of water-soluble and HCl-hydrolyzable N and increased advantageous water retention capacity. PCA also showed that substrates A-E exhibited porosity and water field capacity similar to those of Pr. Substrates F-J had porosity and water field capacity similar to those of BE/S, whereas substrates K O were more similar to Pr and to substrates A and B. The presented data indicate that DMC and MSW separates were complementary in providing good physical and chemical characteristics to the growth substrates.

Direct land application of cement kiln dust- and lime-sanitized biosolids: extractability of trace metals and organic matter quality.

Abstract Direct-land application of biosolids can affect soil organic matter (SOM) quality and be a source of trace metals (TMs) which may then be exported outside soil systems by plants, animals, and surface and subsurface waters. Organic matter (OM) quality and the chemical distribution of Cu, Zn, Cr, Ni, Pb, Co, and As were evaluated in soil amended with cement kiln dust-(CDB) and lime-treated (LSB) biosolids. Forms of these metals were classified by sequential extractions as easily extractable and exchangeable, potentially extractable, and non-extractable. SOM quality was assessed by extraction with diethyl ether (DEE) and chloroform (CHCl 3 ). Soils amended with CDB and LSB contained more TMs than did the control soil. Sequential extractions showed that, after one growing season, easily extractable and exchangeable metals accounted for 1.8% and 0.9% of total metals in CDB-and LSB-amended soils, respectively. On the other hand, potentially extractable and exchangeable metals constituted 53.4% and 59.5% of total TMs in the two soils, whereas non-extractable and non-exchangeable metals made up 44.8% and 39.6% of total TMs in the same soils, respectively. Direct-land application of CDB- and LSB-treated biosolids led to strong modifications of SOM quality as indicated by DEE/CHCl 3 ratios (indicative of the biodegradability of SOM), respectively, although the C and N contents did not change. The results also indicate that the dynamics of TMs are related to the degree of stabilization of the OM.

Co-composting of paper mill sludge and hardwood sawdust under two types of in-vessel processes.

Abstract Recycling of organic residues by composting is becoming an acceptable practice in our society. Co-composting dewatered paper mill sludge (PMS) and hardwood sawdust, two readily available materials in Canada, was investigated using uncontrolled and controlled in-vessel processes. The composted materials were characterized for total C and N, water-soluble, acid-hydrolyzable, and non-hydrolyzable N, extractable lipids, and by Fourier Transform Infrared (FT-IR) spectrophotometry. In the controlled scale process, the loss of organic matter was approximately 65% higher than in the uncontrolled process. After undergoing initial fluctuations in N fractions during the first two days of composting, by the end of the process, concentrations of water-soluble N decreased while those of acid-hydrolyzable and nonhydrolyzable N increased in the controlled process, whereas in the uncontrolled process, water-soluble N increased, but N in the other two fractions decreased continuously, indicating that the biochemical transformations of organic matter were not completed. Data on extractable lipids and FT-IR spectra suggest that the compost produced from the controlled process was bio-stable after 14 days, while the uncontrolled process was not stabilized after 18 days. In addition, FT-IR data suggest the biological activity during composting centered mainly on the degradation of aliphatic structures while aromatic structures were preserved. The co-composting of the PMS and hardwood sawdust can be successfully achieved if aeration, moisture, and bio-available C/N ratios are optimized to reduce losses of N.

COMPOSTING DUCK EXCRETA ENRICHED WOOD SHAVINGS: C AND N TRANSFORMATIONS AND BACTERIAL PATHOGEN REDUCTIONS

Composting of agricultural and domestic wastes is used increasingly to reduce weight, volume, and odor; destroy animal and plant pathogens; and improve the quality of end-products to be used as soil amendments and growth substrates. The objective of this study was to investigate the transformation of C and N and the survival of bacterial populations and pathogenic bacteria during in-vessel composting of duck excreta enriched wood shavings. Two feedstocks, collected on different dates, were composted (C1 and C2) in an enclosed hall system equipped with an electromechanical turner. Temperature was continuously recorded, whereas moisture content and bacterial counts were determined twice a week. Data showed that, although the N content of C2 was only half of that of C1, both materials were fully biostabilized at the end of the composting period as indicated by extractable lipid ratios. In the compost with the low C/N ratio (C1), all bacterial populations were eliminated, whereas fecal streptococci, total coliforms, and gram-negative bacteria were still present in C2 at the end of the composting period. Our results emphasize that the composting of manures and other organic wastes needs to be properly managed to stabilize C and N and to eliminate or reduce bacterial populations.

CHANGES IN LIPIDS AND STEROLS DURING COMPOSTING

Pyrolysis-gas (Py-GC) chromatography was used to characterize organic [(diethyl ether (DEE) and chloroform (CHCl3)] extracts of raw and composted duck excreta enriched wood shavings from two finishing cycles (C1 and C2). Materials were collected on days 0, 8 and 23. C1 contained 1.7 % total N while C2 contained 0.9 % total N. Py-GC-MS (mass spectrometry) showed that the extracts contained n-alkanes (C12 to C32), alkenes (C12:1 to C33:1), n-fatty acids (C12 to C28), unsaturated fatty acids (C18:1 and C18:2), and sterols (chochlestene, cholestadiene, stigmastene, stigmastadiene, stigmastatriene, cholesterol, stigmastanol, stigmastanone, stigmastadienone, 17-methyl dialkylsulfanyl decahydro-1H-cyclopenta [a] phenanthrene, 17-methyl dialkylsulfanyl dodecahydro-1H-cyclopenta [a] phenanthrene, and 17-methyl-17-dialkylsulfanyl decahydro-1H-cyclopenta [a] phenanthrene). Other components identified were prystene, squalene (precursor of cholesterol), phthalic acid, diphenylpropane, diphenylbut-2-ene and 1,3,6 triphenyl hex-4-ene. Our data showed significant changes in the lipid composition of duck excreta enriched wood shavings during composting, which appeared to be related to the total N content of the system.