Two-Stage Conversion of Land and Marine Biomass for Biogas and Biohydrogen Production
Författare
Summary, in Swedish
Popular Abstract in English
Peter is a part-time cocoa farmer who produces cocoa beans that are used for chocolate production. However, he has always wondered about the efficient utilisation of the residual cocoa pods, which seem to contain sugar as they attract bees. He discussed this with a student studying a biological process whereby organic material can be converted to biogas and a residue that can be used as a fertiliser.
This student was studying interesting ways of producing renewable sources of energy such as biogas and biohydrogen from organic materials on land and in the sea, and also a new method of improving fertiliser quality. Abundant marine organic materials such as mussels, reeds and seaweed, which do not compete with food grown on agricultural land, were used to produce biogas. Manure, which is an abundant waste resulting from intensive animal farming, was also used for biogas production. The biogas production system consisted of an anaerobic two-tank system. The reason for using a two-tank process is to separate the fast-growing microbes that break down complex organic material from the slow-growing microbes that produce biogas. In this process, both groups of microbes can grow better than if they were mixed in the same tank. The results demonstrated that biogas production in a two-tank process was efficient for mussels including the shells, seaweed, and a mixture of seaweed and manure, as most of the biogas was produced in the second reactor. In the case of the mussels, the shells remained in the first tank and were then easily removed. In addition, the digestion of a mixture of seaweed and manure reduced the effects of toxic substances such as sulphate and ammonia present at high concentrations in each of these materials. On the other hand, biogas production from the reeds or the manure alone was not efficient in the two-tank process since they degrade slowly. Hence, a one-tank process, which is a simple system to operate (even on farm-scale) could be cost effective for reed digestion.
Biogas production from seaweed and the reduction of contaminating heavy metals were also studied. As the seaweed contains high levels of heavy metals, the digested residue can not be used as a fertiliser. Biogas production and removal of the heavy metals were performed in the two-tank biogas process. During the breakdown of organic matter, the liquid produced ferments or sours, due to acid production. This process favours the release of metals, which can easily be removed. Removal of the metal was performed with a sponge-like material called Cryogel®, which is highly porous and has special metal-binding sites. The resulting liquid, with low heavy metal content, was used for biogas production. It was found that biogas can be produced from seaweed, and that the seaweed liquid, which was rich in nutrients, can replace the nutrients and buffer that are usually added to biogas processes. The heavy metals could be reduced using the two-tank system, but more research is needed before the residue is used as a fertiliser.
Finally, biogas and biohydrogen were produced from wheat straw, which is an abundant agricultural residue that does not compete with food cultivation. Since straw degrades slowly, and has a structure similar to that of reeds, the material was first treated to release the sugars into a liquid. The liquid was then used for biohydrogen production, and the resultant waste from this process was in turn used for biogas production, thus using most of the sugars contained in the liquid. Biohydrogen is produced in a similar, but incomplete process like biogas. The processes were very efficient, resulting in high production rates of biohydrogen and biogas. The only emission from the combustion of hydrogen is water vapour, and the addition of a small amount of hydrogen during the combustion of methane significantly enhances combustion. Hence, the production of such fuels from cheap renewable resources will be very beneficial for the environment and reduce climate change.
In conclusion, exploring land and marine organic materials and the pretreatment of slowly degrading materials can increase biogas production. In addition, the two-tank biogas process was versatile in handling a wide range of organic materials, and can be optimised for the combined production of biohydrogen and biogas. This system also offers the possibility of heavy metal removal to improve fertiliser quality.
The student’s advice to Peter was, thus, to use the cocoa pods for biogas production; providing renewable energy to dry his product especially during the rainy season, avoiding the use of firewood. The residue from the biogas process can also be used to improve vegetable production in Theresia’s farm hence, providing enough vegetables for the family.
Peter is a part-time cocoa farmer who produces cocoa beans that are used for chocolate production. However, he has always wondered about the efficient utilisation of the residual cocoa pods, which seem to contain sugar as they attract bees. He discussed this with a student studying a biological process whereby organic material can be converted to biogas and a residue that can be used as a fertiliser.
This student was studying interesting ways of producing renewable sources of energy such as biogas and biohydrogen from organic materials on land and in the sea, and also a new method of improving fertiliser quality. Abundant marine organic materials such as mussels, reeds and seaweed, which do not compete with food grown on agricultural land, were used to produce biogas. Manure, which is an abundant waste resulting from intensive animal farming, was also used for biogas production. The biogas production system consisted of an anaerobic two-tank system. The reason for using a two-tank process is to separate the fast-growing microbes that break down complex organic material from the slow-growing microbes that produce biogas. In this process, both groups of microbes can grow better than if they were mixed in the same tank. The results demonstrated that biogas production in a two-tank process was efficient for mussels including the shells, seaweed, and a mixture of seaweed and manure, as most of the biogas was produced in the second reactor. In the case of the mussels, the shells remained in the first tank and were then easily removed. In addition, the digestion of a mixture of seaweed and manure reduced the effects of toxic substances such as sulphate and ammonia present at high concentrations in each of these materials. On the other hand, biogas production from the reeds or the manure alone was not efficient in the two-tank process since they degrade slowly. Hence, a one-tank process, which is a simple system to operate (even on farm-scale) could be cost effective for reed digestion.
Biogas production from seaweed and the reduction of contaminating heavy metals were also studied. As the seaweed contains high levels of heavy metals, the digested residue can not be used as a fertiliser. Biogas production and removal of the heavy metals were performed in the two-tank biogas process. During the breakdown of organic matter, the liquid produced ferments or sours, due to acid production. This process favours the release of metals, which can easily be removed. Removal of the metal was performed with a sponge-like material called Cryogel®, which is highly porous and has special metal-binding sites. The resulting liquid, with low heavy metal content, was used for biogas production. It was found that biogas can be produced from seaweed, and that the seaweed liquid, which was rich in nutrients, can replace the nutrients and buffer that are usually added to biogas processes. The heavy metals could be reduced using the two-tank system, but more research is needed before the residue is used as a fertiliser.
Finally, biogas and biohydrogen were produced from wheat straw, which is an abundant agricultural residue that does not compete with food cultivation. Since straw degrades slowly, and has a structure similar to that of reeds, the material was first treated to release the sugars into a liquid. The liquid was then used for biohydrogen production, and the resultant waste from this process was in turn used for biogas production, thus using most of the sugars contained in the liquid. Biohydrogen is produced in a similar, but incomplete process like biogas. The processes were very efficient, resulting in high production rates of biohydrogen and biogas. The only emission from the combustion of hydrogen is water vapour, and the addition of a small amount of hydrogen during the combustion of methane significantly enhances combustion. Hence, the production of such fuels from cheap renewable resources will be very beneficial for the environment and reduce climate change.
In conclusion, exploring land and marine organic materials and the pretreatment of slowly degrading materials can increase biogas production. In addition, the two-tank biogas process was versatile in handling a wide range of organic materials, and can be optimised for the combined production of biohydrogen and biogas. This system also offers the possibility of heavy metal removal to improve fertiliser quality.
The student’s advice to Peter was, thus, to use the cocoa pods for biogas production; providing renewable energy to dry his product especially during the rainy season, avoiding the use of firewood. The residue from the biogas process can also be used to improve vegetable production in Theresia’s farm hence, providing enough vegetables for the family.
Avdelning/ar
Publiceringsår
2012
Språk
Engelska
Fulltext
Dokumenttyp
Doktorsavhandling
Förlag
Printed in Sweden by Media-Tryck, Lund University
Ämne
- Industrial Biotechnology
Nyckelord
- steam pretreatment
- dry digestion
- biogas
- biohydrogen
- Caldicellulosiruptor saccharolyticus
- cadmium
- anaerobic digestion
Status
Published
Forskningsgrupp
- Environmental and Energy Systems Studies
Handledare
- Marika Murto
ISBN/ISSN/Övrigt
- ISBN: 978-91-89627-87-1
Försvarsdatum
29 november 2012
Försvarstid
13:15
Försvarsplats
Lecture Hall B, Sölvegatan 39, Center for Chemistry and Chemical Engineering, Faculty of Engineering, Lund University
Opponent
- Åke Nordberg (Dr.)