Towards the sustainable cultivation of microalgae to produce renewable biofuels and added-value chemicals

Microalgal cultures represent a promising alternative source of biomass for biofuel and chemicals production, since they can reach higher energy yields per area than conventional biomass crops and can be grown on marginal land using waste, saline or brackish water. Their use can thus avoid the food-fuel competition for land, resulting in major economic and social benefits. At the present stage however, major developments are needed for making microalgae-to-biofuels process technologically and economically feasible. With respect to a sustainable microalgal biomass production, the following parameters are thought to be of utmost importance: CO2 concentration; light intensity and quality, photoperiod; photobioreactor design; batch, fed-batch or continuous conditions; possible use of wastewater streams. The purpose of the ongoing research is thus to clearly assess the potential and real influence of these parameters on the quantitative and qualitative production of biomass, lipids and added-value chemicals by several microalgal species; and on their respective productivity, taking into account the probable antagonism between biomass and lipid production, often depending on the nitrogen supply. Several species of microalgae are grown at laboratory scale to compare and contrast biomass yield and lipid productivity. In addition to the potential use of oil for biodiesel production, we are currently working towards demonstrating the technical and economical feasibility of an innovative process for syngas production by hydrothermal processing of microalgae. The process is envisioned as a closed-cycle with respects to nutrients, water and CO2, that are separated and reused for microalgae growth, potentially resulting in a sustainable process.

Enhanced biofuel production from microalgae by adding CO2 to stimulate lipid biosynthesis (biodiesel) and by hydrothermal processing (syngas)

Gabriela Anca Haiduc, Christian Ludwig, David Pauli, Jean-Paul Schwitzguebel, Frédéric Vogel

Introduction: Microalgae cultures represent an attractive source of biomass for biofuel and chemicals production since they can have higher energy yields per area than conventional biomass crops and can be grown on marginal land using waste, saline, or brackish water. Their use can thus avoid the food-fuel competition for land, resulting in major economic and social benefits. At the present stage however, major developments are needed for making microalgae-to-biofuels processes technologically and economically feasible. One substantial technical challenge is the development of cost-effective processes for efficient conversion of microalgae biomass to biofuels. Our research aims to enhance the production of biodiesel and of bio-Synthetic Natural Gas (SNG) from microalgae. Experimental : Several species of microalgae are grown at laboratory scale to compare the yield of biomass and lipid production. In addition to the potential use of oil for biodiesel production, we are currently working towards demonstrating the technical and economical feasibility of an innovative process, “SunCHem”, for SNG production via hydrothermal (HT) processing of microalgae. The process is envisioned as a closed-cycle with respect to nutrients, water and CO2, that are separated and reused for microalgae growth, resulting in unprecedented energy efficiency for both algae and fuel production. The possible effect of increasing injection of CO2 in the growth medium is under investigation, with the aim to mitigate CO2 and enhance biomass production. Results and Discussion: Before the feasibility of the process can be demonstrated several key challenges stemming from its closed-nature need to be tackled. One major challenge is the recycling of nutrient-rich effluents, which upon continuous operation might become enriched in potential toxicants that in turn affect the growth of algae. We demonstrated that the presence of trace metals (Ni, Cr) in the recycled effluent as a result of reactor wall corrosion and catalyst leaching resulted in adverse effect on the growth of microalgae. The effect was directly proportional to the heavy metal concentration, and for the highest concentrations tested (Ni 25 ppm or Cr 5 ppm) complete inhibition of cell growth was observed. It is known that algae, like many other organisms, can adapt to extreme environments, including those with heavy metal contamination, and resulting mutants or strains should be more suited to survive under those particular conditions. The potential of developing and using metal-tolerant mutant microalgae as a biomass source for the SunCHem process is under investigation. Experiments are undertaken to develop Cr- and Ni- tolerant mutants by selective breeding and then comparing the mutants and the wild-type strains for their sensitivity to the heavy-metal contaminated HT effluent and the resulting biomass yields obtained in each case. It is hoped that the use of the metal-tolerant mutants or strains will contribute to the cost-effectiveness of the process by offering an efficient alternative to the use of the more costly setups otherwise needed for effluent clean-up, thus providing a way to avoid the reduction in the biomass yield upon continuous operation of the SunCHem process. On the other hand, metal-tolerant and accumulating microalgae could be used to treat industrial wastewater. Conclusions: Another aspect of utmost importance is the evaluation of the availability for algae of the nutrients contained in the recycled effluents from the process. To this end, microalgae growth experiments will be performed using as sole nutrient source the salt brine delivered from the HT step. The biomass composition with and without recycled input from the hydrothermal process will be characterized. These tests will provide information on the recycling efficiency and speciation of nutrients and will help to identify potential nutrient management issues. If there is significant loss of a given key nutrient, it will have to be replaced in the bioreactor. A candidate for loss through volatilization could be N. Subsequent studies will explore the role of growth media and especially that of nutrients such as N, P, and minerals. Algae growth experiments will be performed using different synthetic media compositions and varying nutrient levels to assess the tolerance of algae to changes in nutrient level and quality. The issue is of special relevance as the possibility of recycling and reusing all the nutrients, including N and P, is a sine qua non condition for closing the loop in the process.

2010

Biofuel production from microalgae by hydrothermal processing

Rizlan Bernier-Latmani, Gabriela Anca Haiduc, Christian Ludwig, Jean-Paul Schwitzguebel, Frédéric Vogel

Introduction: Microalgae cultures represent an attractive source of biomass for biofuel and chemicals production since they can have higher energy yields per area than conventional biomass crops and can be grown on marginal land using waste, saline, or brackish water. Their use can thus avoid the food-fuel competition for land, resulting in major economic and social benefits. At the present stage however, major developments are needed for making microalgae-to-biofuels processes technologically and economically feasible. One substantial technical challenge is the development of cost-effective processes for efficient conversion of microalgae biomass to biofuels. Our research aims to study the production of biodiesel and of bio-Synthetic Natural Gas (SNG) from microalgae. Experimental: Several species of microalgae are grown at laboratory scale to compare the yield of biomass and lipid production. In addition to the potential use of oil for biodiesel production, we are currently working towards demonstrating the technical and economical feasibility of an innovative process, “SunCHem”, for SNG production via hydrothermal (HT) processing of microalgae. The process is envisioned as a closed-cycle with respect to nutrients, water and CO2, that are separated and reused for microalgae growth, resulting in unprecedented energy efficiency for both algae and fuel production. Results and Discussion: Before the feasibility of the process can be demonstrated several key challenges stemming from its closed-nature need to be tackled. One major challenge is the recycling of nutrient-rich effluents, which upon continuous operation might become enriched in potential toxicants that in turn affect the growth of algae. We demonstrated that the presence of trace metals (Ni, Cr) in the recycled effluent as a result of reactor wall corrosion and catalyst leaching resulted in adverse effect on the growth of microalgae. The effect was directly proportional to the heavy metal concentration, and for the highest concentrations tested (Ni 25 ppm or Cr 5 ppm) complete inhibition of cell growth was observed. It is known that algae, like many other organisms, can adapt to extreme environments, including those with heavy metal contamination, and the resulting mutants are better suited to survive under those particular conditions. In the framework of the present COST Action we will investigate the potential of developing and using metal-tolerant mutant microalgae as a biomass source for the SunCHem process. Experiments will be undertaken to develop Cr- and Ni- tolerant mutants by selective breeding and then comparing the mutants and the wild-type strains for their sensitivity to the heavy-metal contaminated HT effluent and the resulting biomass yields obtained in each case. It is hoped that the use of the metal-tolerant mutants will contribute to the cost-effectiveness of the process by offering an efficient alternative to the use of the more costly setups otherwise needed for effluent clean-up, thus providing a way to avoid the reduction in the biomass yield upon continuous operation of the SunCHem process. Conclusions: Another aspect of utmost importance is the evaluation of the availability for algae of the nutrients contained in the recycled effluents from the process. To this end, microalgae growth experiments will be performed using as sole nutrient source the salt brine delivered from the HT step. The biomass composition with and without recycled input from the hydrothermal process will be characterized. These tests will provide information on the recycling efficiency and speciation of nutrients and will help to identify potential nutrient management issues. If there is significant loss of a given key nutrient, it will have to be replaced in the bioreactor. A candidate for loss through volatilization could be N. Subsequent studies will explore the role of growth media and especially that of nutrients such as N, P, and minerals. Algae growth experiments will be performed using different synthetic media compositions and varying nutrient levels to assess the tolerance of algae to changes in nutrient level and quality. The issue is of special relevance as the possibility of recycling and reusing all the nutrients, including N and P, is a sine qua non condition for closing the loop in the process.

2010

Towards the sustainable cultivation of microalgae for the production of biofuels and added-value chemicals

Gabrielle Hack, Christof Holliger, Charlotte Pfistner, Jean-Paul Schwitzguebel

Microalgae represent an attractive source of biomass for biofuels and chemicals production since they can have higher energy yields per area than conventional biomass crops and can be grown on marginal land using waste, saline, or brackish water. Their use can thus avoid the food-fuel competition for land and water, resulting in major economic and social benefits. At the present stage however, significant developments are requested for making microalgae-to-biofuels processes technologically and economically sustainable. The challenges are thus to increase the efficiency of both algae production and conversion into biofuel. The following parameters appear to be critical for sustainable microalgal production: CO2 concentration; light quantity and quality; batch, fed-batch or continuous growth conditions; photobioreactors design; possible use of wastewater streams. The aim of the ongoing research is to clearly assess the influence of these parameters on the quantitative and qualitative production of biomass, lipids and added-value chemicals by several microalgal species, taking into account the possible antagonism between biomass and lipid production, often depending on the nitrogen and key nutrients supply. Another substantial technical challenge is the development of cost-effective processes for efficient conversion of microalgae biomass to biofuels. In addition to the potential use of oil for biodiesel production, we are currently working towards demonstrating the feasibility of an innovative process, for syngas production by hydrothermal processing of microalgae, after the extraction of some chemicals, valuable for food and health. The process is envisioned as a cycle as closed as possible with respect to nutrients, water and CO2, that should be reused - after the hydrothermal process - for microalgae growth, resulting in higher sustainability for both algae and fuel production. Before the feasibility and sustainability of the process can be demonstrated several key problems stemming from its closed-nature need to be addressed. One major challenge is the recycling of nutrient-rich effluents, which upon continuous operation might become enriched in potential toxicants affecting the growth of algae. For example the presence of some trace metals in the recycled effluent as a result of chemical reactor wall corrosion and catalyst leaching seems to have adverse effects on the growth of microalgae. However algae, like many other organisms, can adapt to extreme environments, like those with metals contamination, and tolerant strains should be more suited to survive under such conditions.

2012

Biofuel production from microalgae by hydrothermal processing

Rizlan Bernier-Latmani, Gabriela Anca Haiduc, Christian Ludwig, Jean-Paul Schwitzguebel, Frédéric Vogel

Introduction: Microalgae cultures represent an attractive source of biomass for biofuel and chemicals production since they can have higher energy yields per area than conventional biomass crops and can be grown on marginal land using waste, saline, or brackish water. Their use can thus avoid the food-fuel competition for land, resulting in major economic and social benefits. At the present stage however, major developments are needed for making microalgae-to-biofuels processes technologically and economically feasible. One substantial technical challenge is the development of cost-effective processes for efficient conversion of microalgae biomass to biofuels. Our research aims to study the production of biodiesel and of bio-Synthetic Natural Gas (SNG) from microalgae. Experimental: Several species of microalgae are grown at laboratory scale to compare the yield of biomass and lipid production. In addition to the potential use of oil for biodiesel production, we are currently working towards demonstrating the technical and economical feasibility of an innovative process, “SunCHem”, for SNG production via hydrothermal (HT) processing of microalgae. The process is envisioned as a closed-cycle with respect to nutrients, water and CO2, that are separated and reused for microalgae growth, resulting in unprecedented energy efficiency for both algae and fuel production. Results and Discussion: Before the feasibility of the process can be demonstrated several key challenges stemming from its closed-nature need to be tackled. One major challenge is the recycling of nutrient-rich effluents, which upon continuous operation might become enriched in potential toxicants that in turn affect the growth of algae. We demonstrated that the presence of trace metals (Ni, Cr) in the recycled effluent as a result of reactor wall corrosion and catalyst leaching resulted in adverse effect on the growth of microalgae. The effect was directly proportional to the heavy metal concentration, and for the highest concentrations tested (Ni 25 ppm or Cr 5 ppm) complete inhibition of cell growth was observed. It is known that algae, like many other organisms, can adapt to extreme environments, including those with heavy metal contamination, and the resulting mutants are better suited to survive under those particular conditions. In the framework of the present COST Action we will investigate the potential of developing and using metal-tolerant mutant microalgae as a biomass source for the SunCHem process. Experiments will be undertaken to develop Cr- and Ni- tolerant mutants by selective breeding and then comparing the mutants and the wild-type strains for their sensitivity to the heavy-metal contaminated HT effluent and the resulting biomass yields obtained in each case. It is hoped that the use of the metal-tolerant mutants will contribute to the cost-effectiveness of the process by offering an efficient alternative to the use of the more costly setups otherwise needed for effluent clean-up, thus providing a way to avoid the reduction in the biomass yield upon continuous operation of the SunCHem process. Conclusions: Another aspect of utmost importance is the evaluation of the availability for algae of the nutrients contained in the recycled effluents from the process. To this end, microalgae growth experiments will be performed using as sole nutrient source the salt brine delivered from the HT step. The biomass composition with and without recycled input from the hydrothermal process will be characterized. These tests will provide information on the recycling efficiency and speciation of nutrients and will help to identify potential nutrient management issues. If there is significant loss of a given key nutrient, it will have to be replaced in the bioreactor. A candidate for loss through volatilization could be N. Subsequent studies will explore the role of growth media and especially that of nutrients such as N, P, and minerals. Algae growth experiments will be performed using different synthetic media compositions and varying nutrient levels to assess the tolerance of algae to changes in nutrient level and quality. The issue is of special relevance as the possibility of recycling and reusing all the nutrients, including N and P, is a sine qua non condition for closing the loop in the process.

2010

Enhanced biofuel production from microalgae by adding CO2 to stimulate lipid biosynthesis (biodiesel) and by hydrothermal processing (syngas)

Gabriela Anca Haiduc, Christian Ludwig, David Pauli, Jean-Paul Schwitzguebel, Frédéric Vogel

2010

Towards the sustainable cultivation of microalgae for the production of biofuels and added-value chemicals

Gabrielle Hack, Christof Holliger, Charlotte Pfistner, Jean-Paul Schwitzguebel

2012