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Abstract
It is estimated that the livestock production was responsible for releasing 11.2 % of global total greenhouse gas (GHG) emissions in 2015, with feed production and protein rich feedstock being the largest contributors to these GHG emissions. Protein based “Green Biorefineries” aim to produce a locally sourced and sustainable protein feed from grasses and legumes, that can substitute imported protein-rich animal feed. Herbaceous fibre press-cake is a byproduct in protein concentrate production. Integration of pyrolysis of fibre residue in the framework of the Green Biorefinery may offer substantial economic and environmental benefits.
This Ph.D. thesis focused on investigation of the fundamentals of pyrolyzing herbaceous fibre press-cake, evaluating the biochar characteristics and identifying the engineering challenges. This work also investigated the application of resulting herbaceous biochar as toxin binder in animal feed via in vitro experiments.
Pyrolysis is thermochemical decomposition (above 300 °C) of organic feedstock (e.g. biomass, waste or plastic) in an oxygen-limited atmosphere that does not permit combustion nor gasification to an appreciable extent and generates three main products, namely gas (e.g. CO2, CO, H2, CH4), liquid (tars/oils and water) and solid (biochar).
In this work different herbaceous species, harvests, and processing within the Green Biorefinery were considered as well as a range of pyrolysis conditions. The results showed that fibre processing within the Green Biorefinery affects the resulting biochar more than the type of herbaceous biomass. The pyrolysis temperature had a greater effect on the resulting biochar than the residence time. Generally, all herbaceous biochars had rather uniform characteristics. It has been identified that solvent extraction of herbaceous fibre press-cake prior to pyrolysis might help to improve the economic viability of the Green Biorefinery by producing high value compounds (e.g. fatty acids, vitamins, or sterols) without having a negative effect on biochar production.
To facilitate and optimize the pyrolysis process, production of herbaceous fibre pellets was explored, using a manual single die hand press. The herbaceous pellets had high durability but were prone to abrasion. The pelletization resulted in slightly decreased yields, possibly due to abrasion.
The results showed that a form of carbon activation is necessary for application of the herbaceous biochars as a toxin binder. Steam and carbon dioxide (CO2) activations were compared on the metrics of specific surface area as well as adsorption capacities. Even though the surface characteristics were similar for both types of activated carbons (steam and CO2), the adsorption capacity for methylene blue was significantly higher in CO2 activated samples. Pelletization had no effect on biochar activation and its subsequent use in adsorption experiments.
To evaluate the potential of herbaceous biochars and associated activated carbons as toxin binder in animal feed, in vitro batch adsorption experiments were performed with zearalenone (ZEA) as a model mycotoxin. The herbaceous biochars and the steam activated carbons showed only a minimal adsorption. On the other hand, the CO2 activated samples proved to be effective binders, and at lower initial ZEA concentrations were as efficient as commercial activated carbon. When biochar is used in animal feed on a regular basis, there is a risk of essential nutrients (e.g. vitamins) being adsorbed from the feed. To evaluate the risk of inducing animal malnutrition, the samples were tested for adsorption capacity of astaxanthin (model compound for vitamin A). The results interpretation was limited due to extensive vitamin degradation. Nonetheless, the work demonstrated that the astaxanthin was removed from the solution by the CO2 activated carbons, and the same adsorption was also observed in the commercial activated carbon.
Overall, this work showed a good prospect for pyrolysis integration into the Green Biorefinery concept and production of herbaceous biochars and activated carbons.
This Ph.D. thesis focused on investigation of the fundamentals of pyrolyzing herbaceous fibre press-cake, evaluating the biochar characteristics and identifying the engineering challenges. This work also investigated the application of resulting herbaceous biochar as toxin binder in animal feed via in vitro experiments.
Pyrolysis is thermochemical decomposition (above 300 °C) of organic feedstock (e.g. biomass, waste or plastic) in an oxygen-limited atmosphere that does not permit combustion nor gasification to an appreciable extent and generates three main products, namely gas (e.g. CO2, CO, H2, CH4), liquid (tars/oils and water) and solid (biochar).
In this work different herbaceous species, harvests, and processing within the Green Biorefinery were considered as well as a range of pyrolysis conditions. The results showed that fibre processing within the Green Biorefinery affects the resulting biochar more than the type of herbaceous biomass. The pyrolysis temperature had a greater effect on the resulting biochar than the residence time. Generally, all herbaceous biochars had rather uniform characteristics. It has been identified that solvent extraction of herbaceous fibre press-cake prior to pyrolysis might help to improve the economic viability of the Green Biorefinery by producing high value compounds (e.g. fatty acids, vitamins, or sterols) without having a negative effect on biochar production.
To facilitate and optimize the pyrolysis process, production of herbaceous fibre pellets was explored, using a manual single die hand press. The herbaceous pellets had high durability but were prone to abrasion. The pelletization resulted in slightly decreased yields, possibly due to abrasion.
The results showed that a form of carbon activation is necessary for application of the herbaceous biochars as a toxin binder. Steam and carbon dioxide (CO2) activations were compared on the metrics of specific surface area as well as adsorption capacities. Even though the surface characteristics were similar for both types of activated carbons (steam and CO2), the adsorption capacity for methylene blue was significantly higher in CO2 activated samples. Pelletization had no effect on biochar activation and its subsequent use in adsorption experiments.
To evaluate the potential of herbaceous biochars and associated activated carbons as toxin binder in animal feed, in vitro batch adsorption experiments were performed with zearalenone (ZEA) as a model mycotoxin. The herbaceous biochars and the steam activated carbons showed only a minimal adsorption. On the other hand, the CO2 activated samples proved to be effective binders, and at lower initial ZEA concentrations were as efficient as commercial activated carbon. When biochar is used in animal feed on a regular basis, there is a risk of essential nutrients (e.g. vitamins) being adsorbed from the feed. To evaluate the risk of inducing animal malnutrition, the samples were tested for adsorption capacity of astaxanthin (model compound for vitamin A). The results interpretation was limited due to extensive vitamin degradation. Nonetheless, the work demonstrated that the astaxanthin was removed from the solution by the CO2 activated carbons, and the same adsorption was also observed in the commercial activated carbon.
Overall, this work showed a good prospect for pyrolysis integration into the Green Biorefinery concept and production of herbaceous biochars and activated carbons.
Original language | English |
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Publisher | |
Print ISBNs | 978-87-94253-93-2 |
Publication status | Published - 15 Nov 2024 |
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Biochar produced from bio-refined grass clover pulp for feed and technical purposes
Saner, A. (PI)
01/11/2020 → 31/10/2023
Project: Research