IPCC’s 6th Synthesis report (latest) has called for the immediate removal of carbon dioxide from the atmosphere and has put forth photosynthesis as the best available carbon removal method. Also, carbon dioxide removal (CDR) forms a part of geoengineering, the deliberate manipulation of the atmosphere to abate anthropogenic climate change. While the definition appears to come from the same thought process that has caused such massive and irreversible climate change, a few of the technologies/strategies under geoengineering are eco-sensitive.
The most obvious CDR method is afforestation/reforestation (A/R). But there are obvious challenges with it. It takes a lot of time and costs much money. Therefore, only the largest oil companies are amongst the ones who can do large-scale A/R. Consequently, we need affordable negative emissions technologies (NETs). These technologies capture more carbon dioxide than they emit over their entire lifecycle.
The most talked about NET is direct air capture (DAC), where electricity-driven devices capture CO2 from the air and permanently store them in deep geological formations. While this is an excellent technology in theory, it is one of the most expensive technologies in practice. It costs up to $200 per tonne of CO2 removed. And another aspect to consider is that the carbon dioxide stored in these geological formations has no commercial value.
What if there is a NET based on photosynthesis, is highly scalable, has commercial value, and could cost $0 per tonne of CO2 to deliver?
Answer: vegetal concrete.
Vegetal concrete is a class of building materials made from vegetal matter, such as the stalks of fast-growing plants or residues of mainstream crops. Arguably, the most popular vegetal concrete is hempcrete. It is made using the stalks of the hemp plant and lime or lime-based binder. Hempcrete has predominantly been used for insulation purposes applied in addition to the external walling material. Its biggest draw, however, is that it is carbon-negative.
How? The hemp plant grows using photosynthesis, the natural process that captures sunlight and carbon dioxide to build the plant’s body. After the plant is harvested, the fibres are extracted for various textile applications, and the stalks are chopped into smaller pieces and mixed with lime. All of these steps emit carbon dioxide. But when the net balance is considered, the carbon dioxide captured by the plant matter is higher than the emissions of producing the raw materials, manufacturing hempcrete, transporting it, installing it, dismantling it after the end of life and disposing of it (cradle-to-grave). Since the lime binder mineralises the hemp particles, it does not biodegrade and go back into the carbon cycle. So once hempcrete is produced, it captures carbon dioxide forever.
But there are fundamental drawbacks. While it has excellent thermal properties, it has abysmal mechanical performance. Further, it isn’t very durable and therefore requires regular maintenance. So the only way to use hempcrete is with timber stud frames for low-rise buildings.
What if there existed a vegetal concrete as strong and durable as incumbent materials, is made from crop residues, and is also carbon-negative and thermally insulating? Let’s entertain the idea that such a product exists.
Approximately 2 billion tonnes of crop residues are globally discarded or burnt annually. In a perfect world, if all those crop residues were used to produce vegetal concrete for walling applications, almost 2 billion tonnes of carbon dioxide would be stored within the vegetal concrete walls. A further 9 billion tonnes of carbon dioxide emissions would be avoided by replacing incumbent walling materials. And the improved building energy efficiency would curb billions of tonnes of carbon emissions from reduced energy usage.
In addition, in countries like India, where farmers are amongst the poorest earners, crop residues become a source of revenue. Further, the fibres of the crop residues lend better technical parameters like crack resistance and earthquake resistance.
Vegetal concrete is our secret weapon for solving climate change without compromising progress and development. It is one of the few commodities that are better for the environment to produce more of.
At GreenJams, we did just that. We created Agrocrete®, the world’s first and only verified carbon-negative vegetal concrete for all building types.