The Biotruck sold. I had two voices in my head. One saying “You can’t sell this truck, it’s your life’s work, your home, the embodiment of your ideals. It’s you”. The other voice, far more pragmatically was shouting, “Snatch the cash out of his hands before he changes his mind, you idiot!”. I took the money and watched the truck drive off, clutching on to the last whiffs of cooking oil exhaust as it disappeared over the horizon. For the next few days I kept glancing at the spot where it had been parked, half expecting it to have returned, like a lost dog that manages to sniff its way back to its owners. Instead I contented myself with a great pair of shoes and a broken laptop which came as part of the deal. Jan Carlo is closing down his shoeshop empire in order to wander the globe in a sustainable way. He was quite peeved at first that someone else had trumped him to the idea, but that emotion was soon outweighed by the fact the Biotruck was up for sale on Ebay. He came, slept the night in it, we spent a day haggling and then shook on it and the deal was done.

The journey for the truck will continue.

And the journey for Chris and I continues too. Tomorrow morning we start work in Biotruck IV. Yes. Four. The first one was the truck I drove to Mali using biodiesel made from waste chocolate. The second one was the one we drove to Athens, although this was a “rally” car really. And the third one is now in the hands of Jan Carlo.

The fourth one is parked outside now, loaded up with some old caravan windows, rolls of loft insulation, the solar panels from Biotruck III, a conical tank, lots of old hosing and more junk than I can begin to remember, let alone describe. For a while now I’ve been collecting junk and components that I’ll need to make the new truck, throwing them in the back, and tomorrow the time has come to start making sense of them all.

Firstly I have to fit the PV panels on the roof, just to get them out of the way so I don’t break them while I’m working on the rest of the truck. This requires drilling small holes in the roof which is a bit daunting. This is also tricky because at some point I want to fit roof hatches, a solar collector for hot water, and if there’s space left a roof garden/low profile greenhouse made out of more caravan windows. It’s a big roof, but there’s not really enough space for it all. Perhaps I can live with 360Watts of solar power instead of 480. With the money I could get for two of my six solar panels I might be able to afford an efficient fridge. After the panels, I’ll fit the windows. This requires cutting massive great holes in the side of the van, which is much more daunting.

This truck isn’t going to be all junk. Having learnt some lessons from the last one, I want to pick and chose what bits are recycled, and what parts are new and efficient. The truck itself for instance is only seven years old. It uses only eight litres to do 100km on motorways, less than half of the old Biotruck.

The engine is common rail, hence the better gas mileage, but converting it to run on used cooking oil is consequently a much tougher challenge. I need a fuel delivery pump that can pump cold vegetable oil at the right speed and pressure, and I am still undecided about how to configure the fuel system. Should I use a closed loop system or a traditional twin tank switching system? I spend the evenings sketching diagrams thinking about how I’d use the system, how to build it, and how it could go wrong.

But the engine conversion is still a way off. First I have to insulate the walls with the rolls of insulation made from recycled plastic bottles that YBS Insulation sent me, and finish the interior. The open-plan shower design worked well and I found an old glass fibre tray that needs repairing. The compost toilet was also great, although this time the vent will go out through the roof and I’m using one of Separett’s toilet seats instead of the whole toilet so I can shrink the size of the toilet and cubicle. Space is tighter in this truck. We still have Abaca’s amazing organic mattress but need to build the bed.

The kitchen and the table and chairs I can build with trash. On the drive down to Spain I stopped at Destruck, possibly France’s only caravan scrap yard. There I found the shower tray, the sink and stove unit. Destruck charge €450 to come and collect your caravan if you want to scrap it, then they spend a fair few man hours destroying it with a sledgehammer. They burn the wood, and recycle the aluminium chassis, the copper components, and the stainless steel. In practice they burn a lot of other unpleasant foams too. They were happy to sell me parts I need for not much money and handed me a sledgehammer of my own to remove the pieces I wanted. I came away after 3 hours with priceless window hinges I’d been searching for for days, and a stainless kitchen sink and stove. On the way back up through France I’ll be stopping off to get some roof hatches too.The stuff that’s not got recyclable they sell for pennies.

So this Biotruck represents a shift in philosophy of living purely off waste to a more compromised approach to allow for the benefits of the efficiency of newness. With the same find of cooking oil, I’ll be able to go twice as far, and I’ll be able to get there quicker.

Efficiency is supposedly able to deliver savings of 30% of our global carbon emissions (or more depending on whose figures you believe). And it can save us money too. Perfect, except it actually does the opposite. History has shown that efficiency actually leads to more consumption of energy. Take refrigeration for instance. Since the 1950s refrigeration has become progressively more efficient, and consequently cheaper. The result is that we use much more refrigeration than we used to. Cars now commonly have AC, domestic refrigeration capacity has become bigger, the dependency on cold-chain transportation is much more widespread. We now use much more energy keeping things cold than we ever did in the ’50s because it’s more cost efficient to do so.

Transportation has followed the same trend. Cars that are cheaper to run encourage more and longer journeys. Our sphere of community is spread over vast distances, because we can travel further with less fuel, but the result is we use more of the golden fossil nectar.

This is makes a myth out of the idea that Natural Gas is a carbon cutting solution, for vehicles or power generation.

Making fossil energy more expensive, so its price represents the damage it causes is the only way to encourage viable development of alternatives, and check consumption. But that’s hugely unpopular because it impacts dramatically on quality of life. No politician will do it, but eventually as the stuff runs out the price will climb anyway. It already is.

The fact that I’ll need to scavenge less fuel to travel as far may encourage me to travel more. But I’m not using fossil fuels, so instead of feeling guilty I can go back to smugly polishing my halo.