Aug 30, 2013

Converting Biomass to Hydrogen Fuel

4 min
The utilization of biomass can be traced back thousands of years, when our smart ancestors first started burning wood to make fire, turning a new p...

The utilization of biomass can be traced back thousands of years, when our smart ancestors first started burning wood to make fire, turning a new page in human history. Since then, biomass had become the main source of energy for daily use and greatly contributed to the development of society.

Although the wide application of fossil fuels since the 19th century slowed down the development of biomass related technology, biomass has made a resurgence in the early 21st century due to a growing preference for creating fuels from renewable sources.

As a result, steam reformation technology was developed to convert biomass to hydrogen fuel, which as a fuel possesses higher energy density and is more environmentally friendly when burned than biomass. This conversion technology uses an anaerobic digester to produce methane from biologically treated biomass material such as chaff, wood pulp, trimmings, dung, biomass garbage, etc., followed by using steam methane reforming equipment to produce hydrogen fuel with carbon monoxide as the byproduct, which is also known as syngas.

One important application of hydrogen fuel is using polymer electrolyte membrane (PEM) fuel cells. PEM fuel cells can directly convert chemical energy to electrical energy with water as the only emission, thus minimizing the energy loss and is considered as a “green energy” device. Since they can be operated under a low temperature range (50-100 °C) and are easy to be customized, PEM fuel cells are developed for vehicle, portable and stationary fuel cell applications.

The reactions in PEM fuel cells are hydrogen oxidation and oxygen reduction. To initiate both reactions under low temperature, a platinum catalyst is mandatory, which is considered to be the most active catalyst for the reactions in PEM fuel cells. However, platinum catalysts are very sensitive to the impurities in hydrogen fuel, especially carbon monoxide. Even 30 ppm of carbon monoxide can cause a 48 percent drop in the output cell voltage of a PEM fuel cell1 and 90 percent voltage drop is observed for the existence of 100 ppm carbon monoxide2. Therefore, if we want to use hydrogen fuel produced from biomass by SMR technology, it is necessary to get rid of carbon monoxide in the syngas (20-25 percent in volume) as much as possible.

In order to remove carbon monoxide from the hydrogen fuel generated from biomass, a purification system is employed. Steam is used to trigger a water gas shift (WGS) reaction for oxidizing most of the carbon monoxide to carbon dioxide. However, since the WGS reaction is a reversible reaction, it is very difficult to keep the reaction going at the direction we want when the concentration of carbon monoxide is relatively low (but still higher than the acceptable concentration).

To solve this problem, pressure swing adsorption (PSA) technology comes up and finally increases the purity of hydrogen to more than 99.99 percent. This technology relies on the gas adsorption to solid surfaces under high pressure. Moreover, this adsorption is very selective based on the materials of the solid surface.

Therefore, if an adsorbent bed that can strongly absorb carbon monoxide but not hydrogen as well is placed in the chamber and the syngas previously purified by WGS reaction flows through it, high purity hydrogen can be collected. Meanwhile, since the surface area of adsorbent material is limited, more than one absorbent chamber is needed for the continuous production. To keep the absorption efficiency, a gas release process is necessary while the chamber is not in use.  In light of these issues, system design and modeling become extremely important to efficiently purify the hydrogen fuel.

The most recent technology designed for hydrogen generating by methane (main product generated from biomass by SMR technology) reforming with PSA purification system can treat up to 20000 m3 gas per hour and produce extremely pure hydrogen with up to 99.999 percent purity, meeting standards for PEM fuel cell applications. For example, Verde LLC in Boston has developed this type of system, and made it customizable for different purposes of use, such as to build a home fuel cell station by utilizing highly pure hydrogen generated from biomass.

Think about it: if all the houses along the eastern coast were installed with this biomass-fuel cell station, most people would not have suffered from that long power outage caused by Hurricane Sandy at all. Besides, the integration of such station could reduce a lot of carbon release and finally save our world from global warming effect.

Verde LLC is a technology manufacturer based in Braintree, Mass. Verde LLC specializes in designing and deploying residential, commercial, and industrial scale electrolyzers used for: renewable energy storage, industrial processing, transportation fuel, natural gas plant peaking and cooling, fertilizer manufacture and distributed generation. They have an extensive network with national laboratories, commercial/industrial partners, and universities as well as products in operation around the world. 

1.    C.M. Seymour. L Power Sources 37, 155 (1992)

2.    R.A. Lemons. J. Power Sources 29, 251 (1990).  

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May 13, 2021

All but two UK regions failing on school energy efficiency

Dominic Ellis
2 min
Yorkshire & the Humber and the North East are the only UK regions where schools have collectively reduced how much they spend on energy per pupil

Most schools are still "treading water" on implementing energy efficient technology, according to new analysis of Government data from eLight.

Yorkshire & the Humber and the North East are the only regions where schools have collectively reduced how much they spend on energy per pupil, cutting expenditure by 4.4% and 0.9% respectively. Every other region of England increased its average energy expenditure per pupil, with schools in Inner London doing so by as much as 23.5%.

According to The Carbon Trust, energy bills in UK schools amount to £543 million per year, with 50% of a school’s total electricity cost being lighting. If every school in the UK implemented any type of energy efficient technology, over £100 million could be saved each year.

Harvey Sinclair, CEO of eEnergy, eLight’s parent company, said the figures demonstrate an uncomfortable truth for the education sector – namely that most schools are still treading water on the implementation of energy efficient technology. Energy efficiency could make a huge difference to meeting net zero ambitions, but most schools are still lagging behind.

“The solutions exist, but they are not being deployed fast enough," he said. "For example, we’ve made great progress in upgrading schools to energy-efficient LED lighting, but with 80% of schools yet to make the switch, there’s an enormous opportunity to make a collective reduction in carbon footprint and save a lot of money on energy bills. Our model means the entire project is financed, doesn’t require any upfront expenditure, and repayments are more than covered by the energy savings made."

He said while it has worked with over 300 schools, most are still far too slow to commit. "We are urging them to act with greater urgency because climate change won’t wait, and the need for action gets more pressing every year. The education sector has an important part to play in that and pupils around the country expect their schools to do so – there is still a huge job to be done."

North Yorkshire County Council is benefiting from the Public Sector Decarbonisation Scheme, which has so far awarded nearly £1bn for energy efficiency and heat decarbonisation projects around the country, and Craven schools has reportedly made a successful £2m bid (click here).

The Department for Education has issued 13 tips for reducing energy and water use in schools.

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