Biogas from drainage ditches at EnTrance

The EnTrance facility is hosting a project to test how best to produce biogas from organic waste from ditches and other drainage canals.

EnTranCe

The many drainage ditches in the Netherlands need regular cleaning, a task for which the Water Boards are responsible. Big, black heaps of stinking waste are often dumped at the side of the small waterways. Hans Banning, founder of consultancy company Proces Groningen, has come up with an idea to put this organic material to good use: turn it into biogas using anaerobic digestion. Initial tests were promising: it was estimated that all the waste from drainage ditches in the Netherlands could produce some 85 million m3 of biogas, enough to supply 50,000 homes. Those figures caught the eye of gas trading company GasTerra, which is funding the project. GasUnie will also be involved, as will a number of Water Boards.

Separation

A container will be located at the EnTrance site with two lab-scale 20-litre anaerobic digestion installations inside. These will be used to test what pre-treatment of the waste will deliver the best results, such as heating, mechanical treatment, adding bio-chemicals, several types of bacteria or fungi. ‘’But what we need to do first’’, says Hans Banning, ‘’is to classify the waste into three different sections: green waste, woody waste and dry waste (like reed). All three can be used for digestion, but they are different kinds of biomass and they need to be treated differently. Separation of the biomass from sand, plastic and other contaminants is an important part of the project, because if we want to scale up, we will have to come up with an efficient way of handling the waste material.’’

Baseline

‘’Next’’, he says, ‘’we will do a baseline assessment. For each type of biomass we want to know how much gas is produced without any pre-treatment. We will also look at whether production from these flows is constant enough, because different ditches yield biomass with a different composition, from different plants.’’

Business case

By the end of the year a business case should be presented, with reasonably precise figures about costs, logistics and production. ‘’At the moment we don’t know how this waste compares with maize or sugar beet pulp, for example. But even if it ends up costing money, there might still be a good reason to go ahead. After all, we‘d be producing energy from the lowest grade biomass there is. The next step would be to perform some longer stability tests with larger digestion tanks. The Water Board Friesland (Wetterskip Fryslan) seems keen on hosting such a pilot. If the business case turns out to be a positive one, you could replicate this throughout the country, work with the Water Boards and build up a logistic chain.’’

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