Troubled times call for ingenious solutions and, from green coal to hydrogen-fuelled ships and the birth of "transumption", here are some of the brightest. Lucy Siegle explains the latest ecovations

Prefacing the launch of the fourth Observer Ethical Awards, we've chosen to highlight 20 of the biggest ethical ideas around at the moment, affording some respite to the prevailing jam-side-down version of life on offer almost everywhere else. Because while there might be a paucity of cash and unadulterated resources, one thing we have in abundance is ingenuity. As Nicholas Stern, author of the eponymous Stern Review, puts it: "There are more incentives to invest in energy efficiency during a recession and when oil prices are high." From constraints come great innovations…

It would be disingenuous to suggest that there isn't a sense of urgency about all this, as Emma Howard Boyd, head of socially responsible investing at Jupiter Asset Management – sponsors of the Big Idea award, makes clear: "The urgency of what is required to combat issues such as climate change has not diminished as a result of the current financial crisis. We need big ideas – and it is at times like these, when there is widespread disruption, that we see innovation and new thinking."

Big ideas need not necessarily be a whistle-and-bells hi-tech response. At least one of our Big 20 can be described as an "ancient technique" on loan from the Aztecs. The modern genius lies in its rediscovery and deployment because, while it would be foolish to believe blindly in a silver bullet for all environmental problems, now is absolutely the time for faith in contemporary ingenuity.

Light bulb rating:

5/5 = Most likely to step in and rescue the plan and/or humanity

4/5 = Genius solution, but ever so slightly flawed

3/5 = A little more work, investment and support needed

2/5 = Epoch changing, but only for a niche community

1/5 = A kernel of an ecological solution lies here - one day ...

1. Biochar

In a nutshell: A way of trapping carbon with "green coal".

The clever bit: Any biomass waste – from wood to peanut shells – releases carbon as it decomposes. But it can be burned in a kiln by pyrolysis (an airless burning technique) to create biochar, also known by the soubriquet green coal. The biochar is then dug back into the ground in order to lock carbon into the soil following a system set out by ancient South American civilisations – which exposes the idea as nothing new. What is groundbreaking, however, is using it to mitigate our current predicament – ie, runaway greenhouse gas emissions. According to experts, billions of tonnes of carbon could potentially be sequestered in the world's soils, specifically from agriculture and forestry residual biomass. Biochar appears to lock carbon in for much longer than other forms or sequestration: a plant or tree will only sequester for 15 to 20 years, for example, whereas it seems reasonable to suggest that the biochar system will sequester for at least 100 years. Also, biochar just happens to anchor soil nutrients extremely well at a time when the planet's soils have lost half of their carbon thanks to industrialised agriculture.

Light bulb rating: 5/5

2. Fertilising the ocean

In a nutshell: Dumping iron dust in the ocean to remove carbon.

The clever bit: It is acknowledged that the oceans are the planet's biggest global sink, soaking up 2bn tonnes of carbon every year. Spreading iron dust on ocean waters can in fact trigger huge plankton blooms the size of a small city. The algae would then absorb carbon dioxide from the atmosphere, and when the algae dies, the whole lot sinks to the bottom of the ocean and is sequestered on the seabed. Proponents – notably Victor Smetacek, an oceanographer from the University of Bremen – suggest that it would take just five to 10 ocean-going ore carriers to deposit iron sulphate, a waste product from iron and titanium smelters, into the world's oceans, and that the phytoplankton created would then remove 1 trillion kilograms of CO2 every year.

Light bulb rating: 3/5

3. Benign biofuels

In a nutshell: The biofuels it's OK to like.

The clever bit: The idea was simple: burn plant-derived biofuels such as maize, sugar and corn in engines, then the CO2 released would be offset by the amount of gas absorbed by the plants when they grew. It appeared you could drive oil-free on green gold. Sadly this was a cruel mirage, and when we got close it became clear that the displacement impact of a biofuel boom would lead to the ploughing-up of virgin habitats, giant monocultures, land-rights disputes, and the truly terrible conundrum of whether to feed the world or power the rich world's private – and expanding – car fleet. In a dramatic fall from grace, biofuels crashed and burned.

However, proponents of second-generation biofuels say it's not the idea that is at fault, just the choice of biomass. This time around they advocate using the whole plant and converting waste materials such as cornstalks and leftover sugar-cane fibres into cellulosic ethanol that will then power our lives. This is reliant on a fledgling process: cracking or splitting cellulose into simple hydrocarbons – in effect breaking down complex chains and liberating sugars.

Light bulb rating: 3/5

4. Hydrogen cargo ships

In a nutshell: Emissions-free shipping.

The clever bit: To produce hydrogen-hybrid boats that could turn global shipping and freight from an emissions juggernaut into a zero-emissions glide across the oceans. The unlikely vehicle of revolution – which admittedly is some way off a transatlantic sortie right now – is a former British Waterways maintenance vessel, converted by Birmingham University, named the Ross Barlow. Believed to be the world's first hydrogen-hybrid canal boat, the Ross Barlow's system works by storing hydrogen in lithium hydride powder, which can be topped up when it has been exhausted.

It's clever stuff because researchers have already overcome the two main hydrogen stumbling blocks that have dogged the automotive industry in particular. First, making hydrogen is one thing; storing it safely is another issue entirely. Unlike hydrogen cars, the system on the Ross Barlow barge means that there is no need to carry high-pressure gas or liquid on board – while there has always been a fear that hydrogen cars might, literally, go off like a bomb, the threat of potential explosions has been removed. And there's another advantage: in cars, hydrogen has always proved to be too heavy, but the genius of the boat idea is that heavy hydrogen, in the form of lithium hydride powder, doesn't matter – ships need ballast.

Light bulb rating: 4/5

5. Species relocation

In a nutshell: Giving under-threat species a second home.

The clever bit: You can see why the plight of the mustang, the romantic symbol of the American west, which is under threat from what has been termed "federal euthanasia", caught the imagination of conservationists. The authorities decreed that the 33,000 mustang population roaming free on public lands across the west must be shot down to size (by losing 6,000). Critics contend that this is because they are in competition for food resources with cattle ranching. But the response – to move the mustangs to another part of the country entirely, to a privately funded refuge – has raised a few eyebrows. In many ways this goes against the grain of conservation practices (which are usually geared towards making the best of a bad job, as in the installation of conservation corridors for elephants that work around depleted areas or trouble spots). Pragmatists say it's about cutting your losses and preventing extinction.

Light bulb rating: 2.5/5

6. Radical eco activism

In a nutshell: Green direct action.

The clever bit: The days of eco radicalism – last seen somewhere around Newbury, some time in 1996 – are back, as signified by climate action group Plane Stupid's breaching of the perimeter fence at Stansted airport in December, the scaling of the chimney at Kingsnorth power station by six Greenpeace protestors the previous October, and two largescale Camp for Climate Action gatherings. Grief, fury and rage caused by political indifference and inaction over the rapid decline of the earth's ecosystems and a seeming permanent get-out-of-jail-free card for the main greenhouse gas emitters has spilled over into direct action. Meanwhile the September acquittal of the Kingsnorth Six marked a turning point: their defence argument – they were trying to protest against climate change-induced damage on a far greater scale than the £30,000-worth of chimney damage they allegedly caused – set a precedent.

Light bulb rating: 4.5/5

7. Reinstate the drinking fountain

In a nutshell: The rebirth of bottle-free water.

The clever bit: Saying "no" to bottled water – and the 13bn plastic bottles sold in the UK every year (just 3bn of which are recycled) – is catching on but is still hard work. This begs the question of what happened to all the beautiful fountains, many donated by philanthropists in the 1800s, that were once dotted around civic centres and parks, and when are they coming back? Some community groups, such as Warley Woods Community Trust near Birmingham, are already planning a £75,000 restoration of the park's drinking fountain.

Light bulb rating: 2/5

8. The world community grid

In a nutshell: Your computer does ethical stuff in the background.

The clever bit: The considerable spare capacity of our home computers is used to make lighter work of some of humanity's most important calculations. The idea is simple: while you use a fraction of your machine's capacity to go about mundane stuff, IBM's World Community Grid runs calculations in the background pertaining to molecular mechanics in order to find the next generation of solar cells for Harvard University. Alone, it is estimated, it would take Harvard's department of chemistry and molecular biology computers some 22 years to do the necessary calculations for the Clean Energy Project, but using our spare computer capacity, researchers hope this can be reduced to a matter of two years. Already nearly half a million users have installed the simple software and signed up (worldcommunitygrid.org) to perform calculations that their owners could never understand.

Light bulb rating: 4.5/5

9. Cradle to cradle

In a nutshell: The future of sustainability.

The clever bit: Each year humanity digs up pristine ecosystems to mine and drill for resources. Less than 1% of these materials end up embodied in the things we use, whereas half a trillion tonnes of waste is chucked away to rot, pollute or belch out methane. You would hope there was a less braindead way of proceeding. There is, it's called cradle to cradle (sometimes abbreviated to C2C), a holistic design system that models human industry on nature's processes where there is no waste. How? Well whether you are constructing a running shoe or a brand new Chinese city, C2C dictates that all materials used conform to two types of nutrient classification: technical or biological. Technical nutrients are benign, non toxic synthetics that can be used in continuous cycles without losing their integrity while biological nutrients are organic materials that decompose into the soil, providing enriching nutrients. This is design for "all children, all species, for all time," as US architect, William McDonagh who, along with German chemist Michael Braungart is one of the main C2C proponents, puts it. Their book, Cradle to Cradle was recently published in the UK and demonstrates contempt for the make-things-less-bad approach of the typical green movement. Admittedly the revolution is still focused on product design; to date Chinese construction projects, trainers for Nike, a car, aircraft seats and even nappies – but things are scaling up: the Netherlands government will make all its procurement orders, from cups to cars, C2C by 2012.

Light bulb rating: 4.5/5

10. Carrotmobbing

In a nutshell: Don't boycott – procott instead.

The clever bit: "The problem is that businesses will do anything for money," says 27-year-old US environmentalist Brent Schulkin. "But what if that's also the solution?" In order to find out, Schulkin approached 23 liquor and grocery stores in his San Francisco neighbourhood and asked what percentage of a day's takings each was prepared to invest in energy-efficiency improvements in return for him organising a "mob" of shoppers to visit the store. The rather unprepossessing K&D Market won the bidding with 22%. Using the internet, Schulkin publicised the scheme, then nervously waited to see if any shoppers would turn up. They did. A huge K&D carrotmob spent about $9,000 in two hours, breathing life into the old corporate-social-responsibility adage that corporations with values can translate this into cold, hard cash. Schulkin appears to have hit on a form of activism that could have mass appeal. Ultimately he wants to create carrotmobs so big that they can negotiate with some of the globe's biggest corporations.

Light bulb rating: 3.5/5

11. Ecotarianism

In a nutshell: Counting carbon emissions rather than calories.

The clever bit: The goal is to change your diet to be low carbon and low impact by choosing foods with the lowest environmental overburden or footprint you can find, with the lowest global-warming potential (GWP) and the least chance of messing up the planet via their acidification and pollution potential. Essentially you're looking for the foodstuffs with the lowest energy inputs and the greatest efficiencies in production. For example, forgo meat from ruminants, particularly cows, in favour of pig and poultry that has a lower environmental impact. As sugar refining uses huge amounts of energy, cut your intake of sweets by 50% and eat dark chocolate rather than milk chocolate (which has a big environmental impact).

Light bulb rating: 2/5

12. Zero-waste fashion

In a nutshell: Clothing without the cutoffs.

The clever bit: That fashion is a profligate business is hardly a revelation, but zero-waste fashion sees no need to conform to a system of excess, instead borrowing from Japanese automotive manufacture, phasing out to minimise ecological impact and maximise profits. Based in London, eco-aware Central Saint Martins graduate Mark Liu created the Zero Waste range. Given that fabric widths are standardised, he has calculated that nearly 15% of fabric is wasted during the pattern-cutting process. To avoid this he engineers cuts, prints and pattern repeats so that no fabric is wasted.

Light bulb rating: 2/5

13. Transumption

In a nutshell: Don't buy stuff – lease it.

The clever bit: It's consumerism, but not as we know it, because when transuming you pay for the service rather than the actual product. Therefore you get the benefits of the product, but you will never own it. A good example is the Interface Evergreen carpet available to lease by the month (interface-resource-europe.com). "We sell only the services of the carpet," says the company website. "That's the colour, design, texture, warmth, acoustics, comfort under foot and cleanliness." Immediately this takes the environmental heat out of consuming, as the onus is put on the manufacturer to reuse, recycle and to make products that can easily be disassembled and changed – ie, more sustainable products. Research shows that when the product remains with the manufacturer, there is an incentive to produce more durable goods, as transuming puts the brakes on the shop-to-landfill consumerist cycle. The first buds of this trend are strongly in evidence with the Rent Not Buy movement. Begun in Anchorage, Alaska by particle and nuclear physisicists Mr and Mrs Caius Howcroft, there is now a flourishing UK chapter (rentnotbuy.co.uk).

Light bulb rating: 4/5

14. Rehome a mutt

In a nutshell: Crossbred dogs win best in show.

The clever bit: Last August the BBC documentary Pedigree Dogs Exposed suggested that Crufts, the annual jamboree celebrating canines from an ever-decreasing gene pool, in effect promoted health problems in dogs. While it was suggested that the Kennel Club get its house in order, Pedigree pet foods dropped its sponsorship of Crufts and the BBC chopped it from the schedule. This is in step with global trends. When Barack Obama promised his daughters a new puppy when they moved into the White House, Ingrid Newkirk, president of Peta, didn't miss a beat. "Senator, no one needs to tell you that this country is proud to be a melting pot and that there is something deeply wrong about wanting only a purebred dog. Millions of Great American Mutts – the dog that should be our national dog – are set to die in our nation's overcrowded pounds and shelters for lack of good homes. When you are ready, please adopt a homeless pound puppy."

Light bulb rating: 1/5

15. Backyard sufficiency

In a nutshell: Treating your garden as a source of protein.

The clever bit: Also known as Micro Eco Farming, backyard sufficiency is about exploiting small (and often unpromising) plots of urban land until they yield a bumper harvest. It uses techniques such as vertical horticulture and hydroponics to grow upwards and more intensively. Using pesticides is not an option, so it is by definition organic. Some techniques are low tech and based on the selection of hardy and adaptable crops, such as planting mushroom beds; others are still works in progress, such as growing your own fish. At Aquavision in Devon (aquavisiononline.com), the UK's first organic carp farm, sustainable aquaculture specialist Jimmie Hepburn is busy developing small carp ponds to demonstrate that backyard carp growing for the table is possible.

Light bulb rating: 3/5

16. Hypermilling

In a nutshell: Ultra economical driving.

The clever bit: Hypermilers don't just aim for good mileage, as eco drivers do – they push fuel efficiency to the limit. Some hypermiling tips are just common sense: the correct tyre pressure on your car can chop 10% from your petrol; decreasing your speed from 75mph to 65mph increases fuel economy, and idling the engine is out – it increases emissions by 13% (go to eta.co.uk for more ideas). Other hypermiling absolutes might seem a little more out there, such as driving in soft soles, dispensing with footwear in order to increase pedal sensitivity (to prevent fuel loss) or ridge riding, aka driving with your tyres aligned with the line at the edge of the road to avoid driving through water.

Light bulb rating: 2/5

17. Strategic organics

In a nutshell: Organic pick'n'mix.

The clever bit: Organic production has lots of eco merits, but the thing that made organics the darling of the shopping trolley was the fact that their production ruled out pesticides. But however skewed the economics (critics contend that conventionally produced food does not reflect its true environmental cost), organic produce still attracts a premium. Strategic organic is therefore about prioritising which items need to be organic, and which non-organic (and therefore cheaper) products you can get away with. The bible of Strategic Organic, the US Environmental Working Group report published in October 2008, ranks fruits and vegetables by the amount of pesticides found on each and is based on testing 43,000 products. The 12 types of non-organic produce to be avoided (the "dirty dozen"): peaches are the "dirtiest", followed by apples, sweet bell peppers, celery, nectarines, strawberries, cherries, lettuce, imported grapes, pears, spinach and potatoes. Meanwhile vegetables such as broccoli, asparagus and onions have relatively low levels – so you can get away with non-organic versions. They are the "cleanest" foods, along with avocados, pineapples, mangos, frozen sweetcorn, frozen peas, asparagus, kiwis, bananas and cabbage.

Light bulb rating: 2/5

18. The slow wardrobe

In a nutshell: Dump the concept of "McFashion", rather than the actual garments.

The clever bit: How big is your fashion footprint? From 2003 to 2007, garment prices fell by an average of 10%, and over the past five years the rate of frenzied buying has accelerated. We make room for the new by discarding some 2m tonnes of the old every year, which goes into landfill. The slow wardrobe extends the useful lifespan of the threads already hanging in the national wardrobe while redistributing stockpiled fashion to those who will wear it, with the aim of decreasing today's average annual consumption of 35kg of clothing per person to a more sustainable 7kg. Consumers prioritise longevity by buying trans-seasonal garments (such as a classic jacket) rather than pure fashion and by purchasing as far up the material food chain as they can afford. We also learn to wash and dry clean more sparingly (both decrease lifespans of clothes) and to use specialist services to refashion and/or mend older garments (just 2% of the annual fashion budget goes on mending or servicing clothes, so this needs to be increased). Meanwhile a 2008 YouGov poll found that there are an amazing 2.4bn pieces of clothing unworn for an entire 12 months (many possibly brand new) cluttering up the national wardrobe, which adds up to £10bn-worth of stockpiled fashion. This needs to be redistributed via a system of clothes swap parties and targeted donations before it is chucked in landfill.

Light bulb rating: 3.5/5

19. Precycling

In a nutshell: The bottom has fallen out of the recycling market, so make it your last resort.

The clever bit: Precycling represents the stage before recycling and, unlike recycling, it expends little energy. Precycling happens at the point of purchase, and entails you choosing the product that comes in the least packaging (therefore diverting waste from landfill) or bringing along your own container or bag. Instead of buying packaged sandwiches, for example, take a lunchbox to work, along with cloth napkins and a reusable water bottle.

Light bulb rating: 4/5

20. Ethical texting

In a nutshell: The end of eco-supermarket dilemmas.

The clever bit: Fish stocks are in famously poor health – only 10% of the top predator species, such as tuna, that swam the world's oceans when industrial fishing began 70 years ago are believed to be left. All of which makes shopping for the right fish problematic. American consumers now have the answer to sustainable fish shopping at their fingertips, as the Fish Phone text service spares them from carting around a copy of Bottomfeeder: How to Eat Ethically in a World of Vanishing Seafood by Taras Grescoe – instead they text the designated number. The Blue Ocean Institute monitors 90 seafood species for up-to-the-minute sustainability ratings and will text back either a safe code "green" or a danger code "red", such as for farmed salmon, along with the health advisory warning that indicates the possible presence of PCBs, dioxins and pesticides.

Light bulb rating: 2.5/5