An Introduction to Biomass

After a brief sidestep into the realm of policy with last week’s Green Deal post, we turn our focus back to renewable technology. This week we are looking at biomass.


Biomass is biological matter composed of living, or recently living organisms, which can be burned or broken down by anaerobic digestion to produce energy. Examples of biomass include wood, straw, animal waste, agricultural by-products and energy crops like oilseed rape. Domestic biomass boilers usually burn logs or wood pellets, so this post will be focusing mainly on wood biomass.

Historically, heating homes with wood was the norm. Today, the practice is popular in mainland Europe and the USA. Many houses in the UK have a fireplace, although heating an entire house using biomass is less common. With the introduction of the Renewable Heat Incentive (see the policy section below) the popularity of biomass as a potentially cheap and sustainable way of heating the home is expected to increase.

So how sustainable is biomass? Burning wood or straw releases carbon stored in the plant matter over the course of its lifetime. When fossil fuels are burned, they release carbon absorbed over millions of years. The carbon released by burning biomass is converted into new plant material by photosynthesis, negating the release of the stored carbon. However, it is important to note that wood biomass is only sustainable if the forests it comes from are properly managed. There is a limit on the land area available to grow these fuels, meaning that in the future biomass will be one of several renewable energy sources used to heat our homes.


The Upside

• Biomass is much more environmentally friendly than using coal, oil or gas. Heating the average home using a wood pellet boiler rather than oil would release 10 times less carbon dioxide (CO2) every year.

• Burning logs or wood pellets is generally cheaper than using oil or electricity. If you can harvest your own wood then it will be even more cost efficient. The Energy Saving Trust estimates that replacing an electric heating system with a biomass one can save roughly £630 per year, with a CO2 saving of 7.5 tonnes per year.

• Biomass energy sources are renewable, but we must make sure that they are sustainably managed.

• There are several different types of biomass, so you can choose which one best suits your situation.

• It is possible to use biomass from local sources. This minimises carbon emissions from transportation, and also supports the local economy. Search for local wood fuel suppliers using Log Pile.

• It is easy to store wood pellets in your home, even if you live in a small house. To see an example of a wood pellet stove being used to heat a home, watch this video.

CAT's wood pellet boiler with automated feeder. To the right are our two log boilers.

The Downside

• Installing a biomass system can mean high initial costs. A simple log stove can cost around £500, with an automated wood pellet boiler costing up to £15,000.

• Biomass is a low-carbon technology, but it is not carbon neutral. The harvesting, processing and transportation of materials all contributes to CO2 emissions. Wood pellets require more processing than logs, but they have a lower moisture content so they burn more efficiently.

• It is cheaper to order fuel in bulk, but storing large amounts of  logs can be difficult in smaller homes.


The 2008 Climate Change Act is a legally binding agreement that the UK will reduce its net carbon emissions by 80% by 2050, compared to emissions in 1990. Government policies like the Green Deal and the Energy Company Obligation are all aimed at reducing the UK’s carbon output and encouraging people to embrace less carbon-positive fuel sources.

The Government’s latest scheme is the Renewable Heat Incentive. This will operate on a system similar to the Feed-in Tariffs for wind and solar energy, with householders who take up the scheme being paid for heating their homes using renewable energy. The domestic RHI has yet to be launched in the UK, although the non-domestic scheme has been in place since November 2011. The domestic RHI is expected to be launched this summer. More information can be found on the Government website.

Preceding the launch of the RHI is the RHIPP scheme (Renewable Heat Incentive Premium Payments), giving householders money towards upgrading their heating systems.

A look inside one of CAT's log burners

And did you know…

Over the past year CAT has been building a biomass teaching facility, which has just opened. Approved by HETAS – the regulatory body for biomass installers – CAT now offers Biomass for Installers (HETAS H005). Intended for experienced plumbers and engineers who want to expand into the renewable heating market, Biomass for Installers will enable those in the plumbing and heating sector to move in to the renewable energy field.

In Ofgem’s last quarterly report of 2012 it was noted that 90% of installations done as part of the non-domestic RHI were for biomass boilers. With the imminent roll-out of the domestic RHI, the number of skilled biomass installers required can only increase.


More information on biomass can be found on CAT’s info page.

Is Alternative Technology still relevant today?

Welcome to the latest weekly blog feature! For the next 13-14 weeks we are going to be producing posts on different renewable energy sources. These posts will cover a range of topics from the basics of biomass to the construction of the cities of the future.

We can’t begin a comprehensive series on renewable energy without first addressing CAT’s long and varied history in the field of Alternative Technology. In the early 1970s when the term AT was coined and CAT was created, the world was just opening up to the idea that traditional technology may not be the only solution to global energy problems. Alternative Technology provided an umbrella term for all the systems and designs that moved beyond the confines of the traditional scientific ideas of the time. What people took from AT however, varied hugely, as the minutes from an early CAT meeting shows:

Notes from 7th – 10th November 1974

Throughout AT’s 40 year history no one definition has been universally accepted. Some people may view this as a difficulty, especially when running a centre where ‘alternative’ and ‘technology’ figure prominently in the title. Yet the malleability of AT meant that people took from it what they wanted. CAT built itself upon the term, creating its own mission statement and definition of AT in the process.

So what were Alternative Technologies back in the 1970s? A CAT mission statement from April 1974 outlines some of the intended projects in this area including, but not limited to: wind and water power, solar, gas, energy storage, heat exchangers, distillation and low energy building. It is a testament to the ingenuity and forethought of the early workers at CAT that Alternative Technologies in the 70s have become mainstream ideas today.

Over the years people have argued that renewable energy technology has become so commonplace, the phrase AT is now defunct. And yet the systems and ideas that AT contains, systems and ideas that have proven real world applications, are still seen as the alternative to other, more harmful ways of generating energy. Until such a time when solar, wind and water-based technologies are a familiar site in the UK and around the world, Alternative Technology will continue to be relevant. It may just be that the definition, as it has done many times in the past, will change.

People who question the relevance of Alternative Technology in this day and age should also consider a few other aspects that make AT a worthy proposition. In March of 2012 the Architectural Association in London hosted the AT@40 conference, marking 40 years since the concept gained such interest and momentum. You can read Paul Allen’s account of the conference here. One of the key messages taken from the conference, according to Paul, is the fact that “Alternative Technology focuses on the benefit to humans as well as to economies.” AT provides a different model for supplying energy, one that allows for small-scale solutions suited to individuals or communities.

Installing the first hydro turbine at CAT

Another vital component of the theory is constant self-auditing. Peter Harper, who coined the phrase in the early 1970s, explains how the word ‘technology’ helps to keep AT’s development grounded: “it means that things have got to work; that you submit to the Rules of Nature and cannot simply live in a dream fantasy land.” Alternative Technology is focused on practicality and rigorous testing, one of CAT’s key tenets when it was founded as a ‘living laboratory’ for sustainability, and something it continues to develop to this day.

Looking back at the history of Alternative Technology it is clear that the phrase itself is decidedly unclear. AT is a broad term that with many different definitions, yet it spawned a multitude of ideas and led to the development of non-fossil fuel energy sources. Next week we will start to look at these a little more closely, starting with a post on the Green Deal in relation to renewable energy.


Congratulations to Britain’s leading women in sustainable architecture

Trish Andrews HRH Prince Charles to some of CAT's student modern architecture

We are delighted to see that Blanche Cameron from RESET development and  former tutor at CAT, Trish Andrews tutor on the professional diploma course, Fran Bradshaw a visiting tutor, Anna Surgenor graduate of CAT’s Msc Advanced Environmental and Energy studies , Sue Roaf and Sarah Wigglesworth, course participant in straw bale building have been listed in the Architects  Journal, Women in Sustainable Architecture article.

The list recognises some of the UK’s leading women architects who are working to make sustainability an integral part of building design.  Fran Bradshaw, said: ‘We like people – that’s why and how we design. Together we can make buildings which are both a pleasure and practical to live in, and which use the earth’s resources carefully and imaginatively.’

With many of these women also teaching at universities and influencing our future architects, we could see a lot more good work to come.

Trish Andrews HRH Prince Charles to some of CAT's student modern architecture

Introducing… Euan, our new student blogger


For the next few months Euan will be taking us to the heart of  the Professional Diploma course in Architecture: Advanced Environmental and Energy studies course he is studying at CAT. After each module he’ll write a post letting us know about the highs and lows.

You can read the work of our previous student bloggers here. We’ll also be introducing student bloggers for our other masters courses, Renewable Energy and the Built Environment and Advanced Environmental and Energy Studies.

After completing my Part One qualification at the University of Strathclyde in Glasgow,  I was lucky enough towork in a variety of roles relating to sustainability in architecture. My year out began at a small rural architecture practice in Argyll where I developed a interest in community development, land ownership and sustainable building techniques. This placement led to me becoming involved with a charity in North Glasgow concerned with bettering facilities in a neglected part of the city. I moved back to Glasgow to become more closely involved with this ambitious project and assisted in designing and building a small community space intended to increase community engagement in the area. After my role finished, I ended the year working as a volunteer co-ordinator in Uganda, where I assisted running school building projects for the University of Leeds’ ‘Raise and Give’ program.

At each of these placements I was told by different people about the Centre for Alternative Technology and the Professional Diploma course. After attending the open days I made the decision to study for my part two on the professional diploma course as it seemed to have the staff and the expertise to direct my study towards sustainable architecture.

I have been impressed by CAT in my first few months and I have learned a great deal already during the modules. The staff are very supportive in the periods in between modules and will help with the projects when you’re back home as well as on site. The year group is small enough to get to know everyone very well. We all keep in touch during the study weeks in between modules, share ideas and resources and help each other out. Each time I’ve been to CAT we’ve all had a great time and it feels like we haven’t been away. So far it has been great!

ZCBlog: A response to John Hayes’ comments on wind power

CAT disagrees with John Hayes’ recent comments on the development of wind power in the UK.

As a long industrialised nation, the UK should be doing more than the minimum required to meet its targets. We should be pioneering a shift toward renewable resources, which we can continue to rely on in centuries to come – unlike rapidly dwindling fossil fuels. Wind – which the UK has an enviable abundance of – remains an integral part of that shift.

The Centre for Alternative Technology’s Zero Carbon Britain report shows how we can harvest a substantial share of our energy from wind power. The proposed use of on-shore wind power is much smaller to that of off-shore wind but we do believe that the benefits of on-shore wind farms has yet to yield their maximum potential. Wind power is an established energy source with a proven track record, the UK has significant wind power resources and therefore it should be cornerstone of our energy policy.

We believe that the next stage in the development of on-shore wind should be to increase local benefits by developing structures for increased local investment, to enable developments to share a much higher proportion of the returns with local communities.

Where’s the impact of pads and tampons?


In this series, we’ve been investigating the impacts of various different consumer products, attempting to untangle the complicated webs of production, manufacture and resource use. We’ve told the story of a chocolate Easter egg, a cotton t-shirt, and a paperback book, discovering along the way some fascinating facts about how these products affect our increasingly fragile planet.

This week, we’re going to investigate menstrual products. Unfortunately, however you term them – sanitary products, menstrual products, whatever – it sounds euphemistic; there’s still a culture of shame surrounding the whole experience of menstruation. Leaving aside the awkwardness, however, and the nomenclature, our use – and disposal – of tampons and pads has a considerable effect on the environment. Every year, we discard an average of 200,000 tonnes of waste from menstrual products, a large proportion of which is destined for landfill or the ocean.

In this post, we’ll take a closer look at what tampons and pads are made of, and consider some alternatives. Help us tell the story by leaving comments below!

First off, let’s have a look at tampons. It’s estimated that one woman will use 11,000 tampons in her lifetime, or 22 items for each period. Each tampon is also estimated to take an average six months to break down, so it’s hardly a surprise that a 2010 survey found that for every kilometre of coastline, there were 8.9 tampon applicators (as well as 22.5 pads, liners and backing strips).

The tampon was first developed in the 20s and 30s, around the same time as the re-usable menstrual cup. However, a business model predicated on disposability was much more attractive, and tampons were marketed aggressively, fixating on their supposed hygiene and convenience. However, they’ve long been linked to health problems, most notably Toxic Shock Syndrome.

Made of cotton or a blend of cotton and rayon, a synthetic product made from wood pulp, there are also concerns that tampons could contain dioxins from the bleaching process and pesticides from the cultivation of the cotton. As we discovered in our post about the impact of a cotton t-shirt, cotton production makes heavy use of incredibly dangerous pesticides.

Tampons aren’t classed as medical products, and as such, don’t have to provide detailed product information. The Women’s Environment Network, in their informative report Seeing Red: Sanitary Protection and the Environment explain that tampon manufacture is self-policed by an industry-led body, which doesn’t even require that tampons be sterile.

This lack of information is especially concerning for fragrance-laced tampons, a concept which seems singularly bizarre. As the Campaign for Safe Cosmetics notes, “because the formulas are considered trade secrets, companies don’t have to disclose what’s in fragrance. We know from product-testing that fragrance may contain allergens, sensitizers, phthalates (a class of chemicals that has been linked to hormone disruption, which can affect development and fertility), neurotoxins and synthetic musks (which can also disrupt hormones).”

Disposable pads are a less modern invention than tampons, with the first versions hitting the market in the late 19th Century. Since then, they’ve evolved into something more user-friendly – as examples in the Museum of Menstruation show, earlier iterations required women to wear a belt to hold the pad in place.

However, the modern materials affording such convenience derive from the petroleum industry – therefore, their manufacture takes a dangerous toll on the environment. Pads also take a very long time to break down, leaving a long-term environmental legacy.

Every year, WEN report, the disposables industry spends a whopping £14 million advertising these products to us. The message – that, as WEN put it, “women are somehow dirty and in need of special cleansing products” – reaches 18.6 million women. So it’s hardly a surprise that disposable menstrual products seem necessary, even unavoidable.

However, there are other options. If you’re the crafting type, you can easily find patterns to make your own re-usable pads online. If not, re-usable pads are available to buy online, as well as re-usable menstrual cups.

What are the impacts of the things we buy? Where is the energy used? What are the impacts on other people and the environment?

Where’s the Impact? is an innovative teaching resource exploring the ecological footprint of products. There are literally thousands of processes involved in the production of any given product – to raise awareness about the impacts of production, pupils use a set of cards to tell the story of a product from beginning to end.

Buy Where’s the Impact from the CAT Eco Store 01654 705 959 or email

Become a long term volunteer at CAT


CAT is on the look out for a new bunch of fresh faces to volunteer from March til September 2012. Annually, CAT accepts two intakes of volunteers on six month placements, where they work closely their chosen department and become a part of the CAT community.

We asked some of CAT’s volunteers about their experience of being here; see below for their stories. For more information about becoming a long-term volunteer, follow this link.

Katie was a volunteer in the summer months in the gardens. With a horticultural background, she came to CAT to build on skills she already had and to develop confidence in her abilities as a gardener. During her time working in the gardens, Katie spent two days a week on the display gardens, and three days a week on the produce gardens. Her work helped produce food for the restaurant and staff lunches, as well as maintain the gardens on the visitor’s circuit which educate visitors to CAT about organic growing methods.

Being a part of the CAT community has been important to Katie. As she says, “it’s a hub of interesting people and projects, which is inspiring to be around.” Katie was also a member of site community, the group of CAT staff and volunteers who live on the CAT site, and enjoyed the communal lifestyle, sharing food and resources.

Making the most of the summer months, Katie and the other summer volunteers spent time exploring the surrounding areas. “To be able to live in a UNESCO biosphere is incredible!” Living so close to incredible surroundings of biosphere and nearby Snowdonia national park has been life-changing for Katie, who is staying on to create a series of films about bugs.



Amy is two months into volunteering in education, as well as Zero Carbon Britain. Having just finished a phD in chemistry, Amy was tiring of research and wanted to do something different. While she felt that she had a fairly good knowledge of sustainability issues, she wanted to learn more about the practical side of things. Visiting CAT with a university group in June, Amy was inspired by the atmosphere and feel of the site, as well as the pioneering research project Zero Carbon Britain 2030.

Her tasks as Zero Carbon Britain volunteer sees her write the regular newsletter, as well as give presentations to a variety of different groups. As an education volunteer, she’s currently attending workshops, with a view to leading them herself soon, and doing research that the other educators can use in their work. As Amy says, “no day is the same!”

Enjoying the ample natural beauty around CAT has seen Amy cycle around the nearby estuary, as well as climb a few mountains. Amy’s also enjoyed the social life at CAT, which sees volunteers and staff eat lunch each day together in the much-loved T Chest.

As for the future, Amy’s stint in the education department has already confirmed her interest in moving into environmental education. She says “I’ve really enjoyed thinking about communicating ideas to a range of audiences, not just schools. At CAT, you talk to a group of 10-year-olds one day, and a group of uni students the next.”

Martin has been volunteering in the information department for two months. Having worked for the Green Party, and having previously volunteered with Friends of the Earth and Transport 2000, Martin has long had an interest in sustainability issues. A member of CAT for several years, Martin decided to take a break from his work as a university administrator to deepen his knowledge.

So far, volunteering with information has seen Martin learn more about specific subjects, revise some of the public materials CAT provides, and edit and write web information pages. In the next few months, Martin is hoping to do some video editing. Information, says Martin, is a good position for those who “want to know everything about everything, people with overactive minds!”

Attracted to the area, Martin has always wanted to experience living in a rural community. It is, Martin notes, rather different from living in a city; it’s great “if you want time to think.” Welsh also interests Martin: “the fact that there’s another British language spoken here attracts me to the area; I like hearing the bilingual announcements when I get off the train in Newport.”


Teaching sustainable development and discovering solutions to global food problems

Ensuring the next generation are well equipped for the transition to a zero carbon future the Education department at CAT specialise in delivering Education for Sustainable Development (ESD) at all levels. From October 24th – 30th CAT Education are running short courses in communicating sustainability taking in a breadth of topics such as energy, buildings and food.

Teaching Sustainable Development and Global Citizenship from the 24th – 27th October is designed for teachers of key stage 2 – 3 showing how ESD can be applied in a school environment. The course looks at all issues surrounding sustainability with a strong emphasis on finding solutions to global problems. Participants will learn how to deliver informative, dynamic sessions on sustainable development and global citizenship, adapted to suit their specific subject.

El buey

Food for Thought from the 28th – 30th October looks more in depth at food sustainability and the effect our food production and consumption has on our environment and individual health. Aimed at educators and communicators this course delves into issues far beyond food miles and farting cows. This course is recommended for anyone who would like to deepen their understanding of food sustainability, and play a part in finding local solutions to global problems.

For a broader understanding of what the Education department at CAT gets up to, take a look at our resources page where you can download our teaching resources for free and Footprint Futures, a free online teaching resource for sustainable development useful as a full project or for fun activities on sustainability.

To book on a course please call 01654 704 952 or email You can also complete an online booking form on our  website.

There is also a 10% discount available to anyone booking with a friend or colleague, both will receive the discount, please mention ‘CAT blog’ when booking.

KE007S08 World Bank

The Sex Life of Spiders

Spiders have a really roundabout way of getting on with the task of procreation– male spiders have two modified appendages called pedipalps on the front of their heads which are used to transfer sperm to the female, but unfortunately they produce sperm from the other end of their bodies which means that they have to disappear into a corner and concentrate on the job in hand so to speak and then transfer it to their palps. Then charged up and ready to go they venture out in search of a female. Courtship is fraught with danger for the generally much smaller male and spiders have developed an extraordinary range of techniques to ensure successful mating. The Nursery web spider wraps up a juicy insect in silk and presents it to his spouse and while she is busy unwrapping and eating it he gets on with what he’s come for. Some spiders practice bondage and tie the compliant female down with silken strands before getting on with it.Yet another species attracts a likely female by impressing her with a lively display of break dancing while others serenade their chosen lady with a tune by rubbing their legs together (stridulation). Perhaps most incredible of all some spiders put their spouses in a form of chastity belt after mating to ensure it is only their genes which are passed on–it’s thought that they leave part of their pedipalp which breaks off and forms a plug which means she cannot be mated, but also means that the male has now effectively castrated himself and is no longer of any use in continuing the line. It now makes sound practical sense to donate his body to the female giving her sustenance and converting him into eggs. So there you go—the humble spider has a lot more up its sleeve than it seems.

It’s Spring?… well the birds seem to think so

Mid February and we arrive to a veritable cornucopia of birdsong…

A Song Thrush, Mistle Thrush, Great Tit and the chaffinches were all in full song among the trees and rafters that they call home around CAT, accompanied by the cheerful song of the Robin.

The Song Thrush was really giving everything it had to be the strongest in the choir, but the tinge of sadness in the Mistle Thrushes song still came through, only to be cheered up by the jolly  Robin. The song of Spring has begun, and it promises to become ever more beautiful as the season continues.

The Great Tit sure it is Spring
The Great Tit sure it is Spring

So open the windows or step outside and let the birdsong wake you and convince you of an early spring. The birdfeeders at CAT have started to attract lots of attention from these feathered friends, and hopefully yours will do the same.