Energy production via waste recycling (Ash for energy)

AI Quick Summary

The increasing production of biomass ash is becoming an economic and environmental problem. In the framework of circular economy, the need to 'recycle, use, eliminate' waste, such as greenhouse gas emission, is essential and adds to the energy crisis we are facing.The use of biomass ash as an additive offers the potential to increase methane production and decrease carbon dioxide emmisions by a min. of 10%, while acting as a micronutrient stimulator for the microorganisms in anaerobic digestion process. IntroductionSwitzerland has launched on an energy transition to prevent the use of fossil fuel as an energy source. Woody biomass in the form of logs, pellets, wood chips and waste wood accounts for 85% of all Swiss biomass which is the second most imposrtan renewable source after hydro. However, the thermochemical process applied to convert this woody biomass into energy vectors generates an increased amount of biomass ash which is becomin gan environmental concern.In Switzerland, 75 kt per year of wood ash is produced from which 40 kt per year are from noble wood and are treated as a waste. This waste contains several trace elements and have porous structures that could be beneficial as catalytic systems. Nowadays, most of the wood ash is disposed of in landfill sites which can cause structural instability, water table and soil contamination, and bioaccumulation of heavy metals in food chains. Furthermore, if discharge is not possible in the region, the wood ash is being transfer to available discharge landfill sites using trucks contributing to the use of fuel and greenhouse gases emissions. Additionally, these landfills remain occupied by waste where could be otherwise used (i.e. for agriculture) and the biomass ash waste remains unvalorised. Whereas it would be preferable, in the interests of sustainability and circular economy, to recycle as much as possible.The use of biomass ash as additive in anaerobic digestion to increase methane production is possible. Anaerobic digestion is a well-known efficient process for biogas. Biogas is generated by the digestion of organic matter and it mainly contains methane (50-70%), carbon dioxide (30-50%) and traces of hydrogen sulfide (<1%). The use of substrates such as animal manure containing high organic macromolecules makes its decomposition slow, resulting in low fermentation efficiency and long retention time. In addition, the accumulation of toxic compounds and anaerobic intermediates could lead to lower biogas yields and thus compromise the feasibility of the plant. In this case, it is suggested to empty the anaerobic digesters, which is linked to an increase in profit and start-up costs. The investment and upgrading costs for large-scale biogas utilization make methane recovery unfeasible in most cases.To improve the anaerobic digestion of substrates with a high macromolecular content, many methods have been implemented, such as chemical, thermal, mechanical, ultrasonic and ozone pre-treatment processes, to accelerate the decomposition of the substrate. These pre-treatment methods involve considerable energy consumption and expense, making them less acceptable and less accessible for practical application.Motivation Additive supplementation has shown several advantages, as it is easy to apply at an economical cost without the need to modify the current infrastructure. Biomass ash derived from wood combustion has shown the potential to be used as an additive for anaerobic digestion due to its capability to:1) Stimulate microorganisms via the presence of bioavailable trace elements: the presence of trace elements is important for healthy bacterial growth and thus digestion efficiency. 2) Improve the direct interspecies electrons transfer (DIET) process due to its conductive nature: Due to the conductive nature of wood ash, the DIET process between bacteria and substrate (acetate and/or carbon dioxide) occurs more efficiently resulting to a higher production of methane and higher reduction of carbon dioxide.3) Improve the stability of biofilm formation : Due to its porous structure, the ash can be used as a supporting media for cell attachment resulting to a stronger creation of bacterial biofilms In addition, ash utilization as additive in anaerobic digestion, would minimize the costs associated with its discharge and would reduce the use of landfill sites allowing for alternative use for the land.ObjectivesTo use biomass ash as additive in anaerobic digestion to stimulate the bacterial community and increase biogas production and quality; higher methane content and lower carbon dioxide content.OutcomeIt is expected that the use of wood ash as an additive in anaerobic digestion will decrease carbon dioxide content from the biogas production by a min. of 10% (approx. 0.38 kt/ year from one plant or approx. 900 kt/ year from all plants in Switzerland) by transforming it to methane. OpportunityCan be applied nationally and internationallyCan be applied to any plant sizeNo additional costs or modifications to plant infrastucture are requiredCan have a social impact: energy access, clowing climate change, reducing waste from landfill, repurposing landfill, jobs creation and pollution reduction

Project Idea Metadata

• Project Idea Name: Energy production via waste recycling (Ash for energy)
• Date: 1/30/2023 10:06:08 AM
• Administrators:
  • Xenia Christodoulou

Project Idea Description

Introduction

Switzerland has launched on an energy transition to prevent the use of fossil fuel as an energy source. Woody biomass in the form of logs, pellets, wood chips and waste wood accounts for 85% of all Swiss biomass which is the second most imposrtan renewable source after hydro. However, the thermochemical process applied to convert this woody biomass into energy vectors generates an increased amount of biomass ash which is becomin gan environmental concern.

In Switzerland, 75 kt per year of wood ash is produced from which 40 kt per year are from noble wood and are treated as a waste. This waste contains several trace elements and have porous structures that could be beneficial as catalytic systems. Nowadays, most of the wood ash is disposed of in landfill sites which can cause structural instability, water table and soil contamination, and bioaccumulation of heavy metals in food chains. Furthermore, if discharge is not possible in the region, the wood ash is being transfer to available discharge landfill sites using trucks contributing to the use of fuel and greenhouse gases emissions. Additionally, these landfills remain occupied by waste where could be otherwise used (i.e. for agriculture) and the biomass ash waste remains unvalorised. Whereas it would be preferable, in the interests of sustainability and circular economy, to recycle as much as possible.

The use of biomass ash as additive in anaerobic digestion to increase methane production is possible. Anaerobic digestion is a well-known efficient process for biogas. Biogas is generated by the digestion of organic matter and it mainly contains methane (50-70%), carbon dioxide (30-50%) and traces of hydrogen sulfide (<1%). The use of substrates such as animal manure containing high organic macromolecules makes its decomposition slow, resulting in low fermentation efficiency and long retention time. In addition, the accumulation of toxic compounds and anaerobic intermediates could lead to lower biogas yields and thus compromise the feasibility of the plant. In this case, it is suggested to empty the anaerobic digesters, which is linked to an increase in profit and start-up costs. The investment and upgrading costs for large-scale biogas utilization make methane recovery unfeasible in most cases.

To improve the anaerobic digestion of substrates with a high macromolecular content, many methods have been implemented, such as chemical, thermal, mechanical, ultrasonic and ozone pre-treatment processes, to accelerate the decomposition of the substrate. These pre-treatment methods involve considerable energy consumption and expense, making them less acceptable and less accessible for practical application.

Motivation

Additive supplementation has shown several advantages, as it is easy to apply at an economical cost without the need to modify the current infrastructure. Biomass ash derived from wood combustion has shown the potential to be used as an additive for anaerobic digestion due to its capability to:

1) Stimulate microorganisms via the presence of bioavailable trace elements: the presence of trace elements is important for healthy bacterial growth and thus digestion efficiency.

2) Improve the direct interspecies electrons transfer (DIET) process due to its conductive nature: Due to the conductive nature of wood ash, the DIET process between bacteria and substrate (acetate and/or carbon dioxide) occurs more efficiently resulting to a higher production of methane and higher reduction of carbon dioxide.

3) Improve the stability of biofilm formation : Due to its porous structure, the ash can be used as a supporting media for cell attachment resulting to a stronger creation of bacterial biofilms

In addition, ash utilization as additive in anaerobic digestion, would minimize the costs associated with its discharge and would reduce the use of landfill sites allowing for alternative use for the land.

Objectives

To use biomass ash as additive in anaerobic digestion to stimulate the bacterial community and increase biogas production and quality; higher methane content and lower carbon dioxide content.

Outcome

It is expected that the use of wood ash as an additive in anaerobic digestion will decrease carbon dioxide content from the biogas production by a min. of 10% (approx. 0.38 kt/ year from one plant or approx. 900 kt/ year from all plants in Switzerland) by transforming it to methane.

Opportunity

Can be applied nationally and internationally

Can be applied to any plant size

No additional costs or modifications to plant infrastucture are required

Can have a social impact: energy access, clowing climate change, reducing waste from landfill, repurposing landfill, jobs creation and pollution reduction

The increasing production of biomass ash is becoming an economic and environmental problem. In the framework of circular economy, the need to 'recycle, use, eliminate' waste, such as greenhouse gas emission, is essential and adds to the energy crisis we are facing.

The use of biomass ash as an additive offers the potential to increase methane production and decrease carbon dioxide emmisions by a min. of 10%, while acting as a micronutrient stimulator for the microorganisms in anaerobic digestion process.