potentiel méthanogène. énergie et GES.

potentiel énergétique de la fraction organique des déchets ménagers urbains.

(en cours de traduction)

By now we know that the organic fraction of municipal solid waste OFMSW or household waste degrades biologically under anaerobic conditions and produces methane CH4 and carbon dioxide CO2 in both, landfill sites and anaerobic digestion tanks alike.

Only once the organic matter is completely decomposed=mineralized=degraded methane production will stop. On landfill sites this may take as many as 10 years mainly as the pH is much lower.

Under the controlled and optimized conditions in anaerobic digestion installations (matter pretreated, tanks steered and heated, without contaminants) organic matter decomposes completely within a matter of one month or two.

While we try to capture all methane that is produced in anaerobic digestion tanks and avoid leaks of this powerful greenhouse gas, landfill sites usually exhale 30%, up to 50% and more of their methane potential to the atmosphere, its energy potential is wasted. This is due to the fact that degasification measures, degas pipes and equipment is only being put in place once landfilling has stopped, at the end. Only once the final cover is being applied, most methane can be captured, this can be years into the life of a certain landfill section.

calculating the theoretical biogas potential.

34 million people live in Morocco. 62% is considered to live in urban areas, 21 million people, each produces between 0.8 to 1 kg of solid waste every day, 365 days a year.

That is (with 0.9kg/day/person) 18,900 tons of MSW/day, ~6,900,000 tons/year. It adds up on the daily tally of what collection trucks dump on the controlled and non-controlled landfill sites.

The biggest landfill sites in Morocco are Casablanca/Mediouna with 4,600t/d, Rabat/Oum Azza with 2,500t/day, then Fès, Marrakech, Tanger and Agadir with ~1,000t/d, followed by Meknes, Oujda, Kenitra, Tetouan, Mohamedia, Safi, Laayoune, and many others. Some landfill sites serve several urban agglomerations.

Conservative estimates put the average organic matter content at 65%, with 70% water. With 30% dry matter (DM), this equals to 1,350,000 tons/year. It is the dry matter, more specifically the volatile solids part (VS ~ 83% of DM) of the dry matter that produces biogas and methane.

Based on these numbers, we can do the theoretical calculation.

Two scenarios:

  1. at conservative estimates one ton of VS produces 380Nm3/t of biogas (60% is CH4), that gives some 250 millions norm cubic meters Nm3/year of CH4, 24/7, or about ~29,000 Nm3 CH4/h, which translates into 134MW of electric power that could produce net (after own parasitic consumption) almost 1 billion kWh of clean electricity (985 million kWh, that is 985 Gwh) enough to power 260,000 Moroccan 4 people households all year round.
  2. in a more optimistic methane potential scenario where the biogas yield is expected at 600Nm3/t VS, we achieve an installed generator engine power of 210 MW with annual electricity production of 1,55 TWh of electric energy, enough for 410,000 Moroccan households.

This is the incredible amount of energy that is not being valorized!

wasted energy adds to the greenhouse gas emissions.

So far most methane on landfills, with very few exceptions in Fès, Oujda and Rabat, goes to the atmosphere.

Every year the landfill sites in Morocco emit greenhouse gas emissions between 4,7 and 7,5 million tons of CO2 equivalent.

Morocco’s government has pledged to reduce green house gas emissions by 2030 by 42%. Some waste management solutions harbor excellent ways to help achieve this target, but it is important to create the market, encourage these solutions, incite.

  1. Get serious with degasification installations on landfill sites, by promoting the production of electricity, allowing injection to the grid at proper tariffs that cover expenditures. Capturing methane on old and new landfills is extremely important!
  2. Divert organic matter to anaerobic digestion plants, by promoting 100% sustainable waste2energy solutions, by allowing injection to the grid at proper tariffs that cover waste treatment plant operating costs (read in detail generizon’s solution, no landfilling, no leachate production).

reality.

It is impossible to capture all methane, neither, is there a way we can source separate all organic waste and divert it all to anaerobic digestion plants. 130 MW electric power requires ~200 digesters of 50 tons/day.

On the other side in Germany alone are 10,000 digesters at work!

Yet, we must seek a balance of different valorization, waste treatment and methane capture projects, and we must start somewhere.

generizon can show a way, where to begin, and what can be done today, please read on 20-30 digesters solution for organic waste in Morocco.