Publicação
Composting of agro-food residues: chemical composition, greenhouse gases emissions and compost agronomic value
| Resumo: | Composting has been widely described and accepted as one of the most feasible and viable tecnhologies for processing and valorising agro-industry wastes. Portugal, as member of the European Union needs acomplish the Community goals reducing the amount of waste generate and/or valorising their wastes. Beyond the recycling advantage, the application of the end product improve the soil quality acting as biologic fertilizer, enables carbon sequestration and may allow their use as a sustainable toll on management of soil-borne diseases. There exists, however an environmental risk associated to the process, such a hight warming potential (GWP) owing to the emission of greenhouse gases (GHGs), such as carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) and other gases as ammonia (NH3) and nitric oxide (NO). One of the objectives of the present thesis was to assess the effect of the chemical composition (phenolic and lignocellulosic contents) of the eight diferentt raw materials used on the composting process and on the gases emmited. This evaluation was fullfilled through the physical-chemical analysis of the raw materials, samples mixtures collected along the composting process and final composts. Composting was studied in two sets on 135 L insulated reactors with forced air circulation and with a system that allow the measurement of gases emissions and temperature during the process. In the first composting set, that use different proportions of spent coffee grounds (0 to 40%), all tratments revealed a substantial decrease in total phenolics and total tannins and an important increase in gallic acid. The GHGs emissions were very low and no significant difference between the treatments was registered. Is possible to conclude that that all spent coffee grounds treatments are suitable for composting, but the proportion of 40 % led to better conditions for composting and lower GHGs emissions. In the second composting set, that use different agro-industry wastes (broccoli, chestnut, red grape marcs, white grape marcs, olive leaves) significant variations were observed over time and between the different wastes. The compost obtained with Chestnut wastes and olive leaves led to higher carbon dioxide, methane and nitrous oxide emissions. A positive correlation was found between phenolics and nitric oxide (r = 0.63; p < 0.01) and between lignocellulose and nitrous oxide (r = 0.51; p < 0.05). Its possible to obsserve that a higher content of hemicelluloses in the wastes seemed to entail higher N2O emissions. These results suggest the potential use of wastes rich in lignocelluloses in composting for the purpose of reducing N losses by NH3 and NO emissions After obtaining the final composts we also studied the effect of eight different composts and their chemical composition on C and N mineralization and GHGs emissions by determination of ammonium (NH4 + ) and nitrate (NO3 - ) and measurement of carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) fluxes from amended soils under laboratory conditions. Throuthg the results its possible conclude that mineralization of the C added to the soils was directly correlated to C/N, total phenolic/N, gallic acid/N and NH4 + and negatively correlated with total organic nitrogen (TON) and lignin. N mineralization was only correlated with C/N. All composts enhanced N2O emissions and no significant difference in cumulative emissions were observed between treatments. Finally a biological assay was performed with the objective of test the suppressive potential of four composts (Chestnut, Grape marc, Coffee grounds and Olive) against the soilborne Botrytis cinerea and Fusarium oxysporum with significant impact on lettuce cultivation. The suppressive effect was noticed in Chestnut and Olive with no significant difference between the two doses applied. These treatments also showed significantly higher values of dry matter yields of leaves and roots which denotes their bio-fungicide and bio-fertilizer potential. The results of this thesis could be a useful instrument for planning field scale experiments giving an idea of quantification and quantification of the GHG and soil C and N pools. Overall, the results pinpointed out that the wastes with high lignocellulose contents have additional benefits on the environment in relation to mitigating nitrogen losses. All the composts applied in pot experiments, were found to be beneficial to plant growth. Besides, composts obtained from chestnut wastes and olive leaves are promisors wastes as bio-pesticides supressing Botrytis cinerea and Fusarium oxysporum wilt diseases. |
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| Autores principais: | Santos, Cátia Inês Rodrigues dos |
| Assunto: | C and N mineralisation Composting |
| Ano: | 2019 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Trás-os-Montes e Alto Douro |
| Idioma: | inglês |
| Origem: | Repositório da UTAD |
| Resumo: | Composting has been widely described and accepted as one of the most feasible and viable tecnhologies for processing and valorising agro-industry wastes. Portugal, as member of the European Union needs acomplish the Community goals reducing the amount of waste generate and/or valorising their wastes. Beyond the recycling advantage, the application of the end product improve the soil quality acting as biologic fertilizer, enables carbon sequestration and may allow their use as a sustainable toll on management of soil-borne diseases. There exists, however an environmental risk associated to the process, such a hight warming potential (GWP) owing to the emission of greenhouse gases (GHGs), such as carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) and other gases as ammonia (NH3) and nitric oxide (NO). One of the objectives of the present thesis was to assess the effect of the chemical composition (phenolic and lignocellulosic contents) of the eight diferentt raw materials used on the composting process and on the gases emmited. This evaluation was fullfilled through the physical-chemical analysis of the raw materials, samples mixtures collected along the composting process and final composts. Composting was studied in two sets on 135 L insulated reactors with forced air circulation and with a system that allow the measurement of gases emissions and temperature during the process. In the first composting set, that use different proportions of spent coffee grounds (0 to 40%), all tratments revealed a substantial decrease in total phenolics and total tannins and an important increase in gallic acid. The GHGs emissions were very low and no significant difference between the treatments was registered. Is possible to conclude that that all spent coffee grounds treatments are suitable for composting, but the proportion of 40 % led to better conditions for composting and lower GHGs emissions. In the second composting set, that use different agro-industry wastes (broccoli, chestnut, red grape marcs, white grape marcs, olive leaves) significant variations were observed over time and between the different wastes. The compost obtained with Chestnut wastes and olive leaves led to higher carbon dioxide, methane and nitrous oxide emissions. A positive correlation was found between phenolics and nitric oxide (r = 0.63; p < 0.01) and between lignocellulose and nitrous oxide (r = 0.51; p < 0.05). Its possible to obsserve that a higher content of hemicelluloses in the wastes seemed to entail higher N2O emissions. These results suggest the potential use of wastes rich in lignocelluloses in composting for the purpose of reducing N losses by NH3 and NO emissions After obtaining the final composts we also studied the effect of eight different composts and their chemical composition on C and N mineralization and GHGs emissions by determination of ammonium (NH4 + ) and nitrate (NO3 - ) and measurement of carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) fluxes from amended soils under laboratory conditions. Throuthg the results its possible conclude that mineralization of the C added to the soils was directly correlated to C/N, total phenolic/N, gallic acid/N and NH4 + and negatively correlated with total organic nitrogen (TON) and lignin. N mineralization was only correlated with C/N. All composts enhanced N2O emissions and no significant difference in cumulative emissions were observed between treatments. Finally a biological assay was performed with the objective of test the suppressive potential of four composts (Chestnut, Grape marc, Coffee grounds and Olive) against the soilborne Botrytis cinerea and Fusarium oxysporum with significant impact on lettuce cultivation. The suppressive effect was noticed in Chestnut and Olive with no significant difference between the two doses applied. These treatments also showed significantly higher values of dry matter yields of leaves and roots which denotes their bio-fungicide and bio-fertilizer potential. The results of this thesis could be a useful instrument for planning field scale experiments giving an idea of quantification and quantification of the GHG and soil C and N pools. Overall, the results pinpointed out that the wastes with high lignocellulose contents have additional benefits on the environment in relation to mitigating nitrogen losses. All the composts applied in pot experiments, were found to be beneficial to plant growth. Besides, composts obtained from chestnut wastes and olive leaves are promisors wastes as bio-pesticides supressing Botrytis cinerea and Fusarium oxysporum wilt diseases. |
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