The world’s population is expected to reach 10 billion by 2050. Ten billion people breathing. Ten billion mouths to feed. And still only one planet Earth!

A good time for reflection

 

Animaux et céréales à la base du biométhane
Using farm waste to produce energy.

 

 

It’s safe to say that creating a healthy, accessible, and environmentally sustainable food system is among the main challenges of the coming decades.

The current pandemic has alerted us to the need for food self-sufficiency and proximity of its production. Many governments have made this issue one of their priorities and are taking various measures to promote local and national food production.

This pursuit of the shortest possible field-to-plate supply line also supports another key priority—that of tackling global warming.

 

Waste to the rescue

 

This is where waste becomes our greatest ally.

We obviously need to prevent food waste at the source, but it’s also important at every step of the supply chain. Even though we’re part of the problem, the good news is that we can also be part of the solution.

The figures are alarming! Here are a few stats:

However, the recovery or treatment of any waste products that are currently lost or wasted can be greatly improved.

Further solutions include methods for locally collecting waste from agricultural, crop, or livestock production.

There is still much to learn and to develop in order to achieve the best possible results, but some trailblazers are already forging ahead, notably by participating in what is known as the circular economy. Support for this trend is not only beneficial for the climate, it also clearly promotes self-sufficiency.

In addition, methanation stands as one of the leading solutions for waste treatment.

 

Did you say methanation?

 

The principle of methanation is similar to what takes place in the human body.

As parents, we teach our children to chew slowly so that their bodies don’t get overly taxed and, above all, have more time to trigger that feeling of fullness. We make sure to feed our children a healthy variety of foods such as cereal, vegetables, dairy products, good fats, and good sugars. We also explain to them how their digestive system works and how food moves through the gut.

We tell them that it all starts with the food we put on our plates. We then chew that food to break it down into smaller particles, which travel to the stomach, where digestion takes place, and then on to the intestines, where nutrients are absorbed and assimilated before waste is eliminated from the body.

These are the same steps as in methanation: stockpile (plate), pre-treatment (mouth), digestion (stomach), and purification (intestine).

The similarity stops there, however, since we don’t feed the digester with food products destined for human consumption! Instead, we use organic waste that can just as well come from farms (solid and liquid manure), canteens and restaurants (table scraps), or the agri-food industry (food processing and slaughterhouses).

The digester decomposes organic matter in an anaerobic (oxygen-free) environment. The process releases methane (the principal component of natural gas) and its by-product, the digestate (fertilizer), which are collected.

 

Did you know that it is also possible to digest the sludge from sewage plants? The process is the same, but no homogenization pre-treatment is needed since the sludge is already in liquid form.

 

Vocabulary capsule

 

Un livre ouvert d'oĂč jaillissent des symboles.

 

Let’s pause here to clear up some of the terminology. Depending on the country in which you live, you may be familiar with the term methanation or biomethanation.

Both words are used to describe the same process. Usage has made the term biomethanation popular in Canada and Belgium, whereas methanation is the preferred term in France.

That said, there is nonetheless a preference for the word methanation when it comes to wastewater treatment, and for biomethanation when it comes to anaerobic biological waste treatment, regardless of the country.

Ah, the joys of language and its uses!

 

Four factors that determine the success of a digester or biodigester

 

Methamoly

 

1.The guarantee of a sufficient and regular supply of raw material

The size of the digesters, and thus the return on investment, is first calculated based on the type (classification) and quantity of the waste materials. In Canada, 40,000 tons of waste per year is currently required to ensure the units already in place continue to operate effectively. We are far from the 167 kg per person per year, leaving plenty of room for the development of new projects!

The quality of the end product also depends on the quality of the waste. In fact, certain types of waste have a higher energy output – known as methanogenic power. For example, once transformed, one tonne of edible oil has a methane potential of 784 m3, while one tonne of pig manure only generates 10 m3 of methane.

To ensure efficiency and cost-effectiveness, the development of a methanation project requires partnerships between industry stakeholders and experts that will endure for 20 years.

2. Daily monitoring of recipes for feeding the digester and maintaining a stable gas composition

The ongoing supply of feedstocks also has a considerable impact on the recipe that farmers prepare for the digester (large stomach). Waste of known origin that is received on a regular basis will ensure that the estimated production of renewable natural gas sold to gas networks is in fact achieved.

We live in an industrial world of living systems, and the biological chain will be weakened if it is forced to digest ever-changing, unhealthy foods. Hence the importance of a perfect recipe to ensure healthy, predictable behaviour.

3. Well-controlled, straightforward purification process

Renewable natural gas (RNG) must be tested before it can be injected into the pipeline system, to ensure it meets current specifications. If it does not meet them, the RNG cannot be injected into the network and gets returned to the treatment stage. This means that quality is never an issue, but the quantity sold can be! And if this occurs too often, the digester will generate increasing waste. This is why close monitoring, based on data collected at the digester output, helps ensure optimization of the injection and its flow rate. After a facility has been set up and configured, machine automation will achieve this close monitoring effectively and reliably.

4. Appropriate training to effectively and efficiently use the tool, with particular regard to maintenance

Many farmers, even those who are passionate and dedicated, feel like they’ve switched careers when they step into the world of methanation. And with good reason! They go from spending time with living creatures to control rooms with a set of instructions and data to check. This is why training is provided when facilities are commissioned. Maintenance and operational support in the form of after-sales service contracts is also provided to ensure the digester is operating effectively and efficiently.

 

How do we obtain refined methane?

 

The bacteria in the digester are responsible for decomposing waste to produce biogas and the digestate. Biogas is mainly composed of CO2 (carbon-free) and biomethane (CH4), with traces of other pollutants.

The biogas is then purified into renewable natural gas (CH4). It is also pre-treated to remove water and pollutants such as hydrogen sulphide (H2S) and volatile organic compounds (VOCs). The CO2 can then be separated from the CH4.

 

And how is it used?

Biogas can be used as fuel for motor vehicles and agricultural machines.

It can produce electricity and heat, which can then be used to heat a building.

In our example (the agricultural sector), the refined biomethane will be sold to gas networks. In Canada, that would include companies such as Energir, FortisBC, etc.

It could then be used for homes and businesses connected to these networks.

Green gas

Let’s wrap up on a hopeful note.

  • Remember that this biomethane is recovered, desulfurized, deodorized, in other words, it’s cleaned.
  • It is made from waste that is transformed, repurposed.
  • When mixed with natural gas, it improves the composition, making it cleaner.
  • This helps make our Earth a healthier place.
  • That’s why it’s also called green gas.

We invite you all to embrace this econological solution!

 

Sophie Chainel

Biomethanation: The Why and The How

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