Plant chemistry: The concept of mass balance – definition and principle

To understand the concept of mass balance, we first need to familiarise ourselves with the notion of "biobased material". In short, a biobased material is a material derived from biomass, which can be of plant or animal origin. Many industries are introducing biobased materials into their manufacturing processes, with the aim of minimising their reliance on fossil fuels. This is the case for many sectors, including the automotive, packaging, construction and transport industries.

Oil, coal and natural gas - nowadays, these fossil resources are widely used in a number of industries. What is the issue? These are being depleted worldwide and release large quantities of CO2 , which is the cause of global warming. Against this backdrop, the chemical industry has developed new manufacturing processes to make the transition from conventional petroleum-based chemistry to biomass-based chemistry.

The aim of biobased chemistry is to introduce ingredients derived from biomass (of plant and/or animal origin) into product manufacturing processes. Here are some examples of various resources that can be used as substitutes to fossil fuels:

• Seaweed
• Starch-rich plants, known as "starch crops" (such as maize, wheat and potatoes)
• Sugar-rich plants known as "sugar crops" (such as beet)
• Oil-rich plants known as "oilseed crops" (such as rapeseed, sunflower and soya)
• Fibre-rich plants known as "lignocellulosic crops" (such as straw, flax and wood)
• Plants rich in active molecules (such as vines)
• Organic waste, we can talk about "upcycling" in some cases (such as kiwi leaves)

Renewable resources hold major environmental and technological opportunities. However, moving towards plant-based chemistry holds a technological and societal challenge. Developing alternatives to replace 100% of all petrochemical resources with biobased resources of is a complex process and relies on the development of new supply, logistics and production chains dedicated to the production biomass-based materials.

Therefore, there are several approaches to this transition objective, such as physical segregation - which involves physically separating materials of biobased origin from petrochemical materials throughout the supply chain - and the concept of "mass balance".

Changes in global legislation on quality and the environment, coupled with growing consumer awareness of environmental issues, have prompted manufacturers to adjust their supply, logistics and production chains.

In response to these numerous environmental and economic challenges, the concept of "mass balance" gained more and more interest in a number of sectors, including the chemical industry. This alternative solution aims to make a reasonable and smooth transition from petrochemicals to 100% biomass. The aim is to gradually replace the fossil resources currently used in the supply, logistics and production chains with renewable resources.

In practice, the concept of "mass balance" involves certifying the use of biobased raw materials of during the manufacturing process in place of or in addition to their petroleum-based equivalents. This "mass balance" certification certifies that the supplier has or will introduce a portion of biobased material equivalent to that contained in the finished product purchased.

The "mass balance" approach is certified by various bodies, which issue a label attesting to the good practice of this principle.

Therefore, the biobased content of the final product is not constant. However, the producer guarantees that the quantity of raw material consumed in the manufacturing process of this batch of finished product has been re-injected into the production cycle in its biobased equivalent, thereby increasing the portion of biobased material in its production cycle over time.

Green energy is a good example of the "mass balance" concept. Green electricity is electricity generated from renewable energy sources such as wind, solar or biomass energy. When a customer subscribes to a green electricity offer, it is physically impossible to determine the exact percentage of green electricity delivered to that customer. However, the energy supplier guarantees that the quantity consumed by its customers has been fed back into the global grid as renewable electricity. As a result, the proportion of green energy in the grid increases.

Hence, the "mass-balance" concept addresses a number of issues. Firstly, the use of fossil fuels is reduced, enabling the chemical industry to develop processes that are more environmentally-friendly. Another benefit is that, as well as helping to reduce greenhousegases, the finished product is completely unaffected by this change, and has the same properties and quality as the original product made from petrochemical raw materials.

The "mass balance" concept approach is a pragmatic, step-by-step process that gives raw material producers sufficient time to develop a supply, logistics and production chain dedicated to the production of biomass-based materials. This approach will therefore ensure the transition to the consumption of biobased materials by structuring this circular economy.

Products made using the mass-balance principle have much smaller carbon footprints than their petroleum-based equivalents, thereby reducing greenhouse gas emissions.

As well as helping to replace fossil fuels, the "mass balance" concept is an opportunity for the chemical industry. Thanks to this concept, the biobased chemistry sector is being structured, ensuring a gradual transition from petroleum-based chemistry to biobased chemistry, in order to become sustainable.

This transition is necessary for several reasons:

• Plant resources shall not compete with human food supplies. If it turns out that these biobased materials intended for food use are also used in chemical processes, there is a risk that these resources will be cultivated and then sold to chemical industries, which could lead to food shortages on a local or even global scale. .
• Avoid overproducing by developing mass farming to the detriment of the ecosystem.

This gradual transition will make it possible to develop research, particularly into non-food products (such as the use of materials derived from the upcycling concept). In the long term, this could make it possible to entirely replace fossil fuels by renewable resources, without impacting the food chain and the ecosystem.

Over the next few years, the widespread implementation of the "mass balance" concept should enable the replacement of fossil fuels by renewable resources.