Scientists convert waste toilet paper into electricity

Toilet paper manufactured with a combination of softwood and hardwood trees have long fibers that wrap gives paper strength. The average American uses over 100 single rolls about 21,000 sheets each year.

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Researchers at the University of Amsterdam"s with colleagues from the Utrecht University has implemented first techno-economic analysis of converting waste toilet paper into electricity. In fact, most people usually prefer not to think about it at all. Yet it is a rich source of carbon, containing 70-80 wt% of cellulose on a dry basis.

Solid oxide fuel cells

By establishing new technique increasing resource efficiency and creating a truly circular economy. The cellulose in WTP comes from trees, the electricity produced is renewable. Using WTP as a resource for generating electricity therefore the ultimate waste recycling concept. The Amsterdam region alone generates some 10,000 tons of WTP per year, enough to power 6400 homes.

The Amsterdam-Utrecht research project, led by UvA professors Gadi Rothenberg and Bob van de Zwaan of the UvA"s Van "t Hoff Institute for Molecular Sciences, proposed a simple two-step process for the conversion of WTP, creating a direct route from unwanted waste to a useful product. Master"s student Els van der Roest examined the possibility of combining devices for the gasification of WTP (step 1) with high-temperature solid oxide fuel cells (SOFCs) able to directly convert the WTP-gas into electricity.

Furthermore, the project"s goal was to assess the feasibility of such a WTP-to-electricity system at a scale of 10,000 ton WTP per year, based on real-life parameter values. Using techno-economic analysis methods, the team presented a basic process design, an overall energy balance and an economic study for this concept. Although, data for the experiments and calculations were obtained in collaboration with the Amsterdam waste-to-energy company (AEB).

Leveled cost of electricity

Moreover, the overall electric efficiency is 57%, similar to that of a natural gas combined cycle plant. The leveled cost of electricity LCOE, a measure used for consistent comparison of electricity generation methods is 20.3¢/kWh. This is comparable at present to residential photovoltaic installations.

The system"s capital costs are still relatively high, mainly due to the fuel cell investment costs. But these are expected to decrease as the market for fuel cells develops. The operating costs are relatively low, to the high thermodynamic efficiency (ca. 70%). The researchers expect learning effects could make the system more competitive in future, with an LCOE of about 11 ¢/kWh. The project team concludes that there is a future in turning waste toilet paper into electricity.

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However, no Dutch company or municipal authority has as yet been willing to invest in further development. The team is now considering taking their concept abroad.