MEVE 013: Unit 07 - Microbes in Greenhouse Gases Mitigation

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UNIT 7: MICROBES IN GREENHOUSE GASES MITIGATION

7.1 Introduction

Greenhouse gases (GHGs) such as carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) contribute significantly to global warming. Recent advancements in environmental biotechnology reveal that microorganisms play a crucial role in mitigating GHG emissions through natural processes like carbon fixation, methanotrophy, and denitrification. This unit explores microbial mechanisms in the context of climate change mitigation.

7.2 Objectives

After studying this unit, learners should be able to:

  • Understand climate change and greenhouse gas sources.
  • Explain microbial roles in global biogeochemical cycles.
  • Describe how microbes help sequester or transform GHGs.
  • Evaluate the potential of microbes in carbon and methane management.
  • Identify microbial strategies for mitigating global warming.

7.3 Climate Change

Climate change refers to long-term changes in global or regional climate patterns, mainly driven by increasing levels of GHGs. Its impacts include rising sea levels, extreme weather events, and ecosystem disruption.

7.4 Cause of Global Warming

7.4.1 Source of Greenhouse Gases

  • Carbon dioxide (CO₂): From burning fossil fuels, deforestation.
  • Methane (CH₄): From agriculture (e.g., rice fields, cattle), landfills.
  • Nitrous oxide (N₂O): From fertilizers, industrial processes.
  • Fluorinated gases: From refrigerants and manufacturing.

7.4.2 Can Microbes Help Save the Planet?

Yes, microbes naturally participate in carbon, nitrogen, and methane cycles, thereby influencing the production and consumption of GHGs. Their roles can be harnessed in climate-smart biotechnology.

7.5 Mechanisms to Solve Climate Change

7.5.1 Microbial Communities and the Carbon Cycle

  • Microbes like autotrophs and decomposers help regulate CO₂ levels.
  • Soil microbes degrade organic matter and release or fix carbon.

7.5.2 Microbial Communities and the Methane Cycle

  • Methanogens produce methane under anaerobic conditions.
  • Methanotrophs consume methane as an energy source, reducing emissions.

7.5.3 Microbial Communities and the Nitrogen Cycle

  • Nitrifiers and denitrifiers regulate N₂O emissions by converting nitrogen compounds.
  • Denitrification returns nitrogen to the atmosphere as N₂.

7.6 How Are Microbes Contributing to Global Warming?

  • Methanogens (e.g., Methanobacterium) produce CH₄ in anaerobic environments.
  • Improper waste or agriculture management can lead to excessive microbial GHG production.

7.7 Greenhouse Gases in Soil

  • Soil acts as both source and sink for CO₂, CH₄, and N₂O.
  • Soil microbial activity is influenced by moisture, temperature, organic matter, and oxygen levels.

7.8 Microbes as Carbon Sink

  • Certain microbes sequester CO₂ in the form of organic carbon or biomass.
  • Fungi and actinomycetes contribute to humus formation, locking carbon in the soil.

7.9 What is Sequestration of Greenhouse Gases?

It refers to capturing and storing GHGs, especially CO₂, to prevent their release into the atmosphere. Sequestration can be biological, geological, or chemical.

7.10 Reduction of CO₂ Using Photosynthetic Cyanobacteria

  • Cyanobacteria use CO₂ during photosynthesis and store carbon in biomass.
  • They can be cultivated in bioreactors or wastewater ponds to capture CO₂ from emissions.

7.11 Combating Global Warming Through Biofuels

  • Microbes produce bioethanol, biobutanol, biodiesel, and biogas, reducing dependence on fossil fuels.
  • Algae and yeast are key biofuel-producing organisms.

7.12 Microbes and Global Warming

  • Microbes can both emit and mitigate GHGs.
  • Their potential in bioengineering, restoration, and energy alternatives makes them key players in climate solutions.

7.13 Microbes as Carbon Sink

(Same as section 7.8, emphasizing the dual role of microbes in sequestration and mitigation.)

7.14 Industrial Effluent and Landfill Leachate

  • These wastes contain organic matter that microbes degrade, often producing CH₄ and CO₂.
  • Engineered microbial treatments (e.g., anaerobic digesters) can reduce GHG emissions from these sources.

7.15 What is Sequestration of Greenhouse Gases?

(Repeated section – reinforces understanding from 7.9.)

7.16 Forest and Ocean Sequestration of Greenhouse Gases

7.16.1 The Role of Forests in Climate Change

  • Forest soil microbes assist in carbon storage, decomposition, and nutrient cycling.
  • Deforestation disrupts microbial balance, increasing CO₂ release.

7.16.2 Ocean Sequestration of Greenhouse Gases

  • Marine microbes, including phytoplankton, absorb atmospheric CO₂.
  • Dead marine organisms sink, sequestering carbon in deep oceans.

7.17 Transformation of Greenhouse Gases

  • Microbial bioconversion of CH₄ into methanol.
  • CO₂ fixation into carbohydrates or bio-polymers via microbes.
  • Use of synthetic biology to engineer efficient carbon-fixing microbes.

7.18 CO₂ Sequestration/Assimilation Using Algae

  • Algae convert CO₂ into biomass through photosynthesis.
  • Can be used in biofuel production, animal feed, or soil amendment.
  • Algae-based carbon capture systems are emerging in industrial applications.

7.19 Let Us Sum Up

  • Microbes are integral to the carbon, nitrogen, and methane cycles, making them powerful agents in GHG mitigation.
  • They act as natural carbon sinks, transform harmful gases, and offer bioengineering potential for climate resilience.
  • Biotechnology allows us to harness microbes in sustainable waste management, energy production, and carbon sequestration.

7.20 Key Words (with Definitions)

  • Greenhouse Gases (GHGs)-Gases that trap heat in the atmosphere, contributing to global warming.
  • Climate Change-Long-term alteration in Earth's climate due to natural and anthropogenic factors.
  • Methanogens-Microbes that produce methane under anaerobic conditions.
  • Methanotrophs-Microbes that consume methane, reducing its emission.
  • Denitrification-Microbial process converting nitrates into nitrogen gas, reducing N₂O release.
  • Carbon Sequestration-The process of capturing and storing atmospheric carbon dioxide.
  • Cyanobacteria-Photosynthetic microbes that fix CO₂ and produce oxygen.
  • Biofuels-Renewable fuels derived from biological sources such as microbes or plants.
  • Microbial Sink-Microbial systems that absorb and store GHGs from the environment.
  • Phytoplankton-Microscopic algae in oceans that fix carbon and form the base of marine food webs.
  • Synthetic Biology-Engineering organisms for improved biological functions, including GHG mitigation

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