Here is a fun fact for you: People produce about 10 billion tons of concrete per year, which makes it the second most produced and consumed substance in the world. The first one is water!
Due to its stability, durability, and strength, it is the world’s most widely used material for construction. However, despite all of his advantages, there has been a lot of speculation about the fact that concrete might be actively contributing to greenhouse gas emission.
Because of this, there is a pressing need for construction and other industries to adopt and introduce environmental-friendly materials. With this in mind, the concrete industry has decided to adopt a sustainable and eco-friendly alternative – the green concrete.

What is green concrete?

Traditional concrete uses cement as the main ingredient, which requires electricity and heat to be produced. This is responsible for 50% of CO2 emissions. The other 50% comes from a very demanding process of calcination, which is the transformation of limestone into quicklime. For this reason alone, the Beyond Zero Emissions has published a report which outlines several ways to improve this situation. 
One of them is the green concrete, a form of eco-friendly concrete that is manufactured and produced using waste or residual materials from different industries. It requires less amount of energy for production and thus produces less carbon dioxide. It is also a lot cheaper and more durable than traditional concrete.
The aim of this type of concrete is to lessen the burden on natural resources and increase dependency on recyclable materials. One of the multiple strategies that can be used for creating green concrete is re-using wash water to reduce water consumption. Other strategies include partial replacement of energy-consuming cement with reusable materials like fly ash, silica fume, wood ash, and many more. This is also called geopolymer concrete. 
Different types of eco-friendly materials
Australia is currently the leading country when it comes to using green concrete. Australian researchers have found effective ways to use many different types of eco-friendly materials like:

Ashcrate
Fly ash is a byproduct of the combustion of coal and is discarded as a landfill. However, it can be used for manufacturing green concrete. 
Fly ash is mixed with lime and water, making it strong and durable just like the conventional cement. It can make for a nice environmental-friendly alternative since it leads to reduced CO2 emissions. 
Apart from this, it can also make concrete resistant to bleeding, shrinkage, and alkali-silica reactivity. 

Blast Furnace Slag
This glassy and granular material is produced by quenching molten iron slag from the blast furnace into water or stream. It can replace about 70% or 80% of cement and improve the durability of concrete. Its main advantage is that the production process emits less amount of heat for hydration.

Micro Silica
This material is an ultrafine powder, which is a byproduct of ferrosilicon alloy and silicon production. It improves the durability of concrete and makes it less permeable. Its main advantage is providing stability for structures that are exposed to harsh chemicals.

Recycled Plastic
In Australia, a Ph.D. student successfully used recycled plastic to produce concrete. He replaced the steel with this new eco-friendly material and reduced the CO2 emission by 50%. 

Fiber Cement
Fiber cement is a durable option that reduces the need for replacement parts and materials over a span of decades. It is created by using water, minerals, and air and using the fire to heat the mixture in a filtration process. 
The design is aesthetically pleasing and uses materials that produce less CO2. Fiber cement Fiber cement has already been tested and used in the construction of high-profile structures like the Tiroler Festival Hall in Austria. 

Marine algal biofuel is considered a promising solution for energy and environmental challenges. All macroalgae have biomass that has the potential for bypassing the shortcomings of the first and the second generation of biomass gained from food crops and other sources. In general, macroalgae contain high levels of carbohydrates and have very little to no lignin, which is common for terrestrial plants.

This makes them a very promising source for liquid biofuel production via bioconversion. Scientists agree that macroalgal biomass can undergo fermentation and other processes in order to be effectively used for potential bioenergy production. While seaweed farming is considered eco-friendly in many ways, these strategies come with its own set of problems and obstacles.

Seaweed farming

So far, seaweed farming has been used primarily as a food source. This is particularly the case in Asia, while in recent years, it made its way to Europe and the US.

Seaweed farming can be divided into two categories: artificial culture and mariculture. Artificial culture requires cultivating seaweeds in a controlled environment, while mariculture uses the natural habitat of shallow lagoons as the perfect place for seaweed beds.

However, recent scientific research has shown that seaweed farming can be much more than just a food source. Currently, bioenergy is produced from various sources like corn and wood. But this takes a lot of space, resources, energy and creates a lot of pollution problems. Seaweed, or macroalgae farming, is considered to be the least environmentally damaging form of aquaculture. It requires little to no input of fertilizers, fresh water sources, medicines, and does not cause any major physical alterations or pollution of the environment.

Companies at the forefront of this idea view oceans as largely untapped resources and potentially a much better source of renewable bioenergy. The general idea behind seaweed farming is to use what is already there. The ocean is vast and will not compromise the needs of the population. Once harvested, the scientists can use various chemical processes to produce biogas, ethanol, and other forms of energy.

Bioenergy conversion

The conversion of macroalgae to bioenergy can be divided into two processes: thermochemical or dry and microbiological or wet process.

The thermochemical process uses heat to promote the chemical transformation of macroalgae biomass into energy. The microbiological process uses microorganisms to make or modify biomass to produce bioenergy. Once harvested, seaweed has to go through several other processes like direct combustion, pyrolysis, gasification, trans-esterification, hydrothermal liquefaction, saccharification, and fermentation in order to be converted to biofuel. To determine the yield and the properties of biofuel that is produced, it is important to know the chemical composition of macroalgae, the pre-treatment method used, conversion conditions and the characteristics of microbes involved.

Since macroalgae are rich in carbohydrates, this makes them most suitable for biogas, biobutanol, and bioethanol products. Furthermore, it is easy to examine the content of macroalgae for triacylglycerol, which is the best indicator for the suitability of the algae for biodiesel production. Macroalgae come with a high conversion rate and high percentage of fatty acids, which makes them a perfect candidate for producing bioenergy. However, some algae may also have a high concentration of metal, sulfur, and nitrogen, which may catalyze the process. So far, scientists have successfully farmed seaweed in shallow lagoons. Sadly, it produced very little bioenergy, and the harvesting took 2 to 3 months.

Problems associated with producing bioenergy with seaweed farming

To produce enough bioenergy, large-scale farming is needed. The problem experts are facing right now is that large seaweed beds will occupy the extensive marine area and can potentially alter natural habitats. There is also the problem of light, nutrients, carbon, and kinetic energy absorption in deep dark parts of the ocean. All components are required for successful seaweed farming. While technology is being developed, concerns are raised regarding the effect on many components of natural communities like bacteria, fish, macrofauna, and corals. This is why the construction of large and complex seaweed farms is still in the planning phase.

Producing bioenergy with seaweed is definitely possible. But before this turns into a viable option, further research is needed to determine how to deal with potential environmental risks associated with the development of large-scale seaweed farming.

Conversations around the environment seem to have been placed on the back burner of late amid the global pandemic. While the grounding of many planes, and the lockdowns of the world’s cities, gave the appearance of the world healing itself there is no denying that in a bid to safe the spread of Covid – 19 the suitability rules have been flung out of the window – single use products are back with a bang and taking the car alone is deemed safer than using public transport, but at what is that to the environment?

Even though the cries for climate action have been masked in recent months there is still great comfort to be taken from knowing the good fight continues and one of the companies vying for a place at the top of that billing is direct air capture technology (DAC) Swiss start-up Climeworks.

The company was founded by Christoph Gebald and Jan Wurzbacher as a Spin-off from ETH Zurich. So far they have raised CHF 120 million in investment and have 14 plants throughout Europe from Iceland to Italy, they are ten years into their projects and are becoming big contenders in the DAC market.

Climeworks direct air capture plants capture CO2 with a patented filter and are powered by either waste or renewable energy. The air-captured carbon is sold to customers in the food, beverage and agriculture, and renewable fuels and materials markets.

The project in Iceland removes the carbon dioxide from the air and stores it safely and permanently underground. The carbon dioxide is removed with a technology called direct air capture, mixed with water, and pumped around 700m underground. “With the specific geological circumstances that you have up in Iceland, within a year or two, pretty much all the co2 that has been pumped underground is mineralised and stored there in the form of calcite rocks,” says Climeworks Chief Operations Officer, Dominique Kronenberg.

Climeworks introduced a service on their website where customers can pay a subscription to offset their own carbon emissions.

“We were able to prove that customers, both private people and corporates, were willing to buy our carbon dioxide removal service,” continues Kronenberg, “this was the kind of change that we felt coming over the last couple of years but it wasn’t something that we foresaw when we started the company.”

“The customers that we currently have are pioneering customers that have a strong belief that a technology like ours is needed to reverse climate change. They have a strong feeling that what we do and how we do it is the right way and they would like to support our mission by subscribing to our service. In their name, we permanently remove carbon dioxide from the air and give them access to immediate and direct climate action,” he says.

Blessed are we that companies like Climeworks make it possible for us to take responsibility for our impact on the planet and give something back in the fight to slow down climate change.

Climeworks are on a mission to inspire 1 billion people to remove carbon dioxide from the air.