Marine phanerogams, mangroves and swamps
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Blue carbon: nature-based techniques to control the impact of anthropogenic activities

The carbon sequestered in coastal soils can stay trapped for centuries due to the water saturation allowing for a sustained carbon build-up, giving them a role to play in climate change mitigation

Nature-based treatment techniques can remediate the impact of anthropogenic activities

Since the Industrial Revolution, the CO2 levels have been rising, and the Met Office, the national meteorological service for the U.K., predicted that in 2021 the atmospheric carbon dioxide (CO2) concentration will reach 417 parts per million (ppm), fifty percent higher than pre industrial levels based on data collected at the Mauna Loa Observatory in Hawaii.

Industrialization and Urbanization caused soil heavy metal pollution, as after the 1950s, anthropogenic heavy metal inputs in the pedosphere increased (Hernandez, Probst A, Probst JL, Ulrich 2003). Harnessing ecosystems’ intrinsic restorative capacity through nature-based solutions can mitigate climate change and pollution and help ecosystems cope with a changing climate.

Nature-based treatment techniques can remediate the impact of anthropogenic activities and improve the state of stressed ecosystems. A study conducted by the international NGO The Nature Conservancy and fifteen other institutions like Cornell University, the Swedish University of Agricultural Sciences, and the University of Aberdeen shows that implementing natural climate solutions (NCS) such as the restoration of degraded soils and the conservation of wetlands could deliver thirty-seven percent of the emissions reductions needed to keep global warming below two degrees Celsius by 2030.  

Soil plays a role in climate change adaptation and mitigation through carbon sequestration

As this service decreases the presence of Carbon Dioxide (CO2) in the atmosphere. Carbon is found in the atmosphere, in the terrestrial biosphere, which includes soil, plants, and animals, and in the ocean. The total carbon (C) stored in terrestrial ecosystems amounts to about 3170 gigatons (Gt).

Soils constitute the principal reservoir of terrestrial carbon (Lal 2008), storing 2344 Gt of organic C (Stockmann et al., 2013), around eighty percent of the total. The majority of the soil organic carbon (SOC) is stored in the boreal biomes of Northern Eurasia and North America, in wetland soils, and in the permafrost and peat in Arctic areas.

The first meter below the ground level contains around 1417 Pg of Carbon, and the above-below ground vegetation and dead organic matter store 456 Pg of Carbon. Through photosynthesis, CO2 is removed from the atmosphere and accumulated in the soil carbon pool through a process called soil carbon sequestration.

Soil can store or release carbon depending on the soil conditions and the activity of the soil organisms, which includes megafauna, macrofauna, mesofauna, microfauna, and microflora. About forty percent of the living organisms in the terrestrial ecosystems interact with soils during their life cycle.

Soil organic carbon (SOC) loss is the conversion of organic carbon stored in the soil into carbon dioxide (CO2) or methane (CH4). Researchers from the Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California, Berkeley have found that a four degrees Celsius heating of soils to one hundred cm deep would result in a thirty-seven percent increase in the carbon dioxide release (Hicks Pries, Castanha, Porras, Torn, 2017).

Blue Carbon – the carbon sequestered in marine and coastal ecosystems

Marine and coastal ecosystems like mangroves, salt tidal marshes, and seagrass meadows give a contribution to climate change attenuation, which makes their preservation a necessary part of the global climate change mitigation and adaptation strategy.

These ecosystems are located in every continent except Antarctica. Around the world, 171 nations host at least one coastal blue carbon ecosystem (mangroves, tidal marshes, and seagrasses). All three ecosystems are present at once in seventy-one countries.

At least twenty-one percent of the global area of blue carbon ecosystems and fifteen percent of global blue carbon assets are part of the fifty marine sites included in the UNESCO’s World Heritage List, such as the Dutch Wadden Sea Conservation Area, the German Wadden Sea National Parks of Lower Saxony and Schleswig-Holstein, and the majority of the Danish Wadden Sea maritime conservation area.

Via their living biomass aboveground, living biomass below-ground, non-living biomass, and soil, these ecosystems sequester carbon from the atmosphere and the ocean. The carbon sequestered in these ecosystems is called ‘blue carbon’ (Duarte et al., 2005). 

The report The Ocean as a Solution to Climate Change: Five Opportunities for Action, commissioned by the High-Level Panel for a Sustainable Ocean Economy, states that the protection and restoration of mangroves, seagrass, and salt marshes offer the most beneficial combination of carbon mitigation and social benefits among the five examined typologies of ocean-based climate action implemented to decrease GHG emissions (Hoegh-Guldberg O et al.).

The elevated water saturation present in coastal soils and their anaerobic state allow coastal ecosystems to trap carbon for extended periods, resulting in significant carbon stocks. Acting as carbon sinks, coastal ecosystems with their plants and the sediment below help mitigate climate change.

In the United Kingdom alone, shelf seas store an estimated 205 million tonnes of carbon (Luisetti et al., 2019). On a global level, the preservation of seagrass beds, salt marshes, and mangroves could deliver carbon dioxide (CO2) mitigation amounting to one-point-eighty-three billion tonnes. An estimated 340 000 to 980 000 hectares of coastal ecosystems are destroyed each year (Murray et al., 2011). 

As the conversion and degradation of coastal ecosystems can result in a release of CO2 from these environments to the oceans and the atmosphere (Donato et al. 2011), the effects of climate change and human development can hinder coastal ecosystems’ action as carbon skins, impacting these environments’ long-term resilience and jeopardizing the effectiveness of blue carbon projects.

Long‐term adaptive management, the control of environmental stressors, coastal squeeze management, and further research can safeguard coastal ecosystems against sea levels rise and extreme climatic events, preventing the reversal of carbon sequestration, the exacerbation of ocean acidification, and the loss of the services provided by coastal and marine ecosystems.

Coordinated by Conservation International (CI), the International Union for Conservation of Nature (IUCN), and the Intergovernmental Oceanographic Commission of the United Nations Educational, Scientific, and Cultural Organization (IOC-UNESCO), the Blue Carbon Initiative is an integrated global program formed in 2011. The project strives to mitigate climate change by conserving, restoring, and promoting the sustainable use of coastal marine ecosystems worldwide.

Blue carbon: carbon dioxide sequestered by coastal and marine ecosystems
Blue carbon is the carbon dioxide that is naturally sequestered by coastal and marine ecosystems, image rps group

The need of rewilding British seas for biodiversity and blue carbon 

In their report Blue Carbon – Ocean-based solutions to fight the climate crisis, released in May 2021, the Marine Conservation Society and Rewilding Britain have highlighted the need of rewilding British seas for biodiversity and blue carbon as part of the strategy to reach net zero emissions by 20250, calling for the rewilding and protection of at least thirty percent of the British seas by 2030. 

A lagoon is a shallow body of water with limited inflow and tidal flow separated from larger bodies of water by a barrier like an island, a peninsula, or a reef. Transitional zones between land and sea, lagoons can be connected to the near body of water through an inlet.

Their area ranges from less than 0.01km2 to more than 10,000 km2. Lagoons are located in warm temperate, mediterranean, or dry subtropical areas along sheltered, non-steep, or non-rocky coasts. They occupy fifteen percent of the world’s shorelines.

Coastal lagoons are productive ecosystems (Knoppers, 1994; Duck and da Silva, 2012) that provide an array of services, delivering cultural, ecological, and socioeconomic benefits. They promote the health and productivity of coastal waters, areas, and ecosystems, including mangroves, salt marshes, and seagrasses.

Lagoons contribute to biodiversity by providing essential habitats for a variety of shellfish and fish species. Compared to other aquatic ecosystems, coastal lagoons support high rates of primary production and secondary production. Primary producers like phytoplankton and aquatic plants flourish in coastal lagoons, thanks to these areas’ low flushing rates. 

Coastal lagoons filter suspended matter, regulate dissolved oxygen, perform the decomposition of organic matter, remove pollutants, and recycle nutrients. Climate change is expected to impact wetland ecosystems to a greater degree than oceanic or terrestrial ecosystems in areas that contain commercial, industrial, or residential structures.

Where plant communities are subjected to environmental stressors derived from human activities that can be heightened by climate change and its consequences (Keddy, 2000). Sea level rise, changes in weather patterns, and salinity threaten all the aquatic plant community types that are located in the proximity of the oceans, and losses are likely to occur in un-managed and unprotected wetland plant communities (Short, Kosten, Morgan, Malone, Moore, 2016).

Wetland and aquatic ecosystems can be reshaped by climate change, as temperature influences their productivity, changing the ecosystems’ thermal suitability as aquatic habitats for resident plant and animal species, warping the current species distribution in aquatic ecosystems (LeRoy Poff, Brinson, Day, 2002). 

Bioremediation techniques 

Bioremediation processes are nature-based treatment techniques that employ plant species and microbes’ natural ability to absorb and degrade the targeted hazardous substances, mimicking the natural depuration processes that occur in natural ecosystems and utilizing nature’s ability to manage and restore ecosystems. 

Bioremediation technologies can be used in synergy with other physical and chemical treatment methods to manage diverse groups of xenobiotic pollutants found in the soil, water, or atmosphere. Bioremediation can tackle a broad range of compounds and relies on the applied environmental parameters that affect microbial growth and the degradation rate.

Bioventing, Bioattenuation, Biosparging, Composting, Landfarming, and Phytoremediation techniques fall under the umbrella of bioremediation. Phytoremediation techniques utilize living plants, soil, and associated microorganisms to clean up soil, air, and water polluted by hazardous contaminants by reducing the load of toxins in the targeted site. 

Bioremediation is utilized to minimize the impact of the pollutants produced by anthropogenic activities, and it can’t degrade inorganic contaminants (Shah, 2014). Bioremediation techniques can be used to lessen the environmental and health impact of oil spills, acidic mining drainage, crime scenes, and underground pipe leaks. In non polluted conditions, microorganisms such as bacteria, fungi, and protists, break down organic matter (Speight 2018).

Bioremediation operates by presenting these pollution-eating organisms with fertilizer, oxygen, and other conditions that promote their growth. A series of critical contingencies are needed for a successful bioremediation process, as their absence causes the microbes to grow at a slow pace or perish.

These conditions include a pH ratio ranging between six-point-five and seven-point-five, carbon as the energy source for microbial life, and host-microbial contaminants such as nitrogen, phosphorus, sulfur, and potassium, which provide energy to the microbes, promoting their growth.

Other factors essential to eradicating persistent pollutants from a targeted site via bioremediation processes are optimal temperature, water or moisture, and oxygen when using contaminants that require aerobic environments such as Acinetobacter, Flavobacterium, Nocardia, Pseudomonas, Rhodococcus, Sphingomonas, and Mycobacterium. 

The conditions of a site can be bettered by supplying it with amendments that range from chemicals that produce oxygen to chemical mixtures like molasses and vegetable oil. Factors such as cost, site characteristics, variety, and concentration of the contaminants determine the amount of time necessary to carry out a bioremediation process, which depending on the circumstances, can take from several months to multiple years.

Bioremediation processes can occur ex-situ, where the contaminated material is taken from a site and brought to a treatment location, or in-situ, where the bioremediation process is carried out in loco at the contamination site (Fennell, Du, Liu, Häggblom, Liu 2011).

Phytoremediation is a bioremediation process that employs various species of hyper-accumulator plants and their rhizospheric microorganisms to neutralize, remove, transfer or stabilize xenobiotic contaminants found in the soil and groundwater.

Certain plants used in Phytoremediation techniques such as phytostabilization, phytostimulation, phytotransformation, phytofiltration, and phytoextraction can break down organic contaminants through the release of toxin-degrading enzymes into the soil; others can extract pollutants and degrade them inside their tissues (Beans 2017), where they store non-biodegradable contaminants like metalloids.

Heavy metal (Hms) tolerant and hyper-accumulator plants are classified as such when they exhibit rapid growth, high biomass, and can extract and accumulate significant amounts of HMs in their tissues (Krame, 2010).

Botanical families such as the Brassicaceae, Poaceae, Fabaceae, Asteraceae, Salicaceae, Chenopodiaceae, Cyperaceae, Amaranthaceae, Cannabaceae, Cannaceae, Typhaceae, Pontederiaceae, and Careophylaceae (Gawronski S.W., Gawronska H., 2007) include species that can be employed for phytoremediation processes.

Common water hyacinth
Common water hyacinth (Eichhornia crassipes), photography Ted Center, Agricultural Research Service, USA

The Water hyacinth and lagooning – a bioremediation waste-water treatment technique

Native to South America, the Water hyacinth is a fast-growing, perennial, free-floating aquatic weed of the aquatic flowering plants family Pontederiaceae. It is capable of assimilating large quantities of trace elements and heavy metals and it is employed in lagooning, a bioremediation waste-water treatment technique.

It became known in Europe in 1823 when it was found and recorded by the German naturalist C. von Martius while studying the Brazilan Flora. Since the twentieth century, the water hyacinth has been considered an invasive aquatic plant due to its rapid growth rate and ability to spread and form thick layers over the water surface, causing poor water transparency and threatening local aquatic biodiversity.

The European Union in July 2016 banned any sales of the water hyacinth in EU countries. The water hyacinth absorbs and digests the pollutants present in wastewater such as biochemical oxygen demand (BOD), heavy metals like arsenic, chromium, and mercury, organic matter, pathogens, and suspended solids (Ingole, Bhole 2003 and Lissy P N, Madhu 2011). 

Green Keeper Africa is a Beninese company that designs, manufactures, and markets organic absorbers and is the leading African producer of industrial absorbents. Created in 2014 by David Gnonlonfoun and Fohla Mouftaou, Green Keeper Africa utilizes the properties of the Water Hyacinth to control and manage the leakage of polluting industrial products.

They use water hyacinth as the raw material to manufacture Gksorb, an absorbent fiber, and the first African-made industrial absorbent. Gksorb can absorb a variety of industrial liquids, including dyes, crude oil, and heavy fuel oil with an absorption rate of 1200%; as certified by the Centre of Documentation, Research and Experimentation on Accidental Water Pollution (CEDRE).

A French non-profit-making association and international reference body that certifies the properties of pollution control products. Green Keeper Africa’s Hyacinth Fiber was tested according to AFNOR and ASTM standards, can be incinerated after use, and employed as an alternative fuel for cement industries.

By utilizing an invasive aquatic plant as raw material, Green Keeper Africa promotes the use of neglected agricultural resources and the short-term reduction of poverty and gender inequalities in the communities where the water hyacinth harvesting is carried out, as the majority of the workers employed by Green Keeper Africa are local women. 

Hemp operated for phytoremediation

 Like the Water Hyacinth, hemp is operated for phytoremediation in contaminated areas due to its ability to tolerate high heavy metals content in soil and accumulate HMs in its tissues, as shown by several studies. Hemp (Cannabis sativa) is an annual herbaceous flowering plant of the family Cannabaceae.

Its cultivation in China dates back to 2800 BCE, and it was introduced in the Mediterranean Basin during the Roman Empire. Hemp is linked to various industries that use its fiber to manufacture textiles, rope, bioplastics, insulation material, and biofuel.

The BIO SP.HE.RE (Bio Integrated Spirulina and Hemp Remediation) project intended to test from a scientific viewpoint the ability of the combined application in Phytoremediation of Arthrospira platensis, a filamentous gram-negative cyanobacterium, and hemp to improve the two plants ability to extract heavy metals from polluted soils and water. 

The project was co-financed by the Apulian region and carried out by ApuliaKundi in collaboration with Innovative Solutions, a company linked to the Polytechnic of Bari, and Enjoy Farm, a cooperative created to promote green economy.

About the partnership: ApuliaKundi, Innovative Solutions, Enjoy Farm

«Hemp is suitable for phytoremediation projects as it can tolerate high pollution levels in the form of a high heavy metal content or the presence of a significant amount of organic contaminants. These compounds, which pose health risks and environmental concerns to our communities, are nutrients for hemp plants, which thrive in contaminated sites.

Another characteristic that makes hemp a viable candidate for phytoremediation projects is its versatility of use at the end of the phytoremediation process. The plants employed to clean up a site can be utilized by the construction industry and for fuel production through incineration in waste-to-energy facilities.

As the hemp plants cannot absorb the entirety of heavy metal found in the polluted site, the amount of HMs they contain complies with the national laws and regulations, allowing for their employment as construction material.

Incinerating the hemp plants that socked up heavy metals and stored them in their tissues would allow us to recover these compounds that, once refined through electrochemical processes, can be put back into the production cycle, which is advantageous from an environmental, social, and economic perspective.

This process would follow the principles of atom economy and green chemistry. Through mining, we scatter the heavy metals that nature condensed in a site throughout millennia. With Phytodeuration, we do the opposite by collecting them in the facilities.

The use of these hemp plants in textile production is unideal, as it would be ill-advised to expose the skin to heavy metals through direct contact with the fabrics». Explains Vito Gallo, project coordinator of BIO SP.HE.RE, president of Innovative Solutions and associate Professor of chemistry at the Technical University of Bari in Apulia, Italy.

«During our project, we recorded that the use of Arthrospira platensis caused an increase in biomass, facilitating plant growth in polluted water and soil».

Vito Gallo 

PhD is an Associate Professor at the Technical University of Bari (POLIBA) and a member of the Department of Civil, Environmental, Land, Construction and Chemical Engineering.

Roberta Fabbrocino

The writer does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article.

check and buy on Prototipo Store
item collections in limited edition
crafted according to our editorial search

Hemp / made in Italy
Lampoon is working to restore Hemp production in Italy
as hemp is the one and only natural vegetal fiber sourceable in the country
for more info, please email us

check and buy on Prototipo Store
item collections in limited edition
crafted according to our editorial search

Hemp / made in Italy
Lampoon is working to restore
Hemp production in Italy
as hemp is the one and only
natural vegetal fiber sourceable in the country
for more info, please email us at [email protected]

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