We all relied on tips to make our jobs as tour guides worthwhile. My then girlfriend called me disgusted to tell me about an American passenger that hadn’t coughed up in the usual way. Instead of the recommended $3/day this septuagenarian had given her some chocolate and a pair of nylon tights.

It seems the oldtimer had been to Italy once before, as a GI in the 1940s. In those days a Hershey bar, stick of gum, and a pair of stockings curried a lot of favour with Italian girls. Now in his 70s he’d had the forethought to pack some American treats with him when he’d left Iowa, presumably with the intention of rekindling those good times.

My ex didn’t know whether to be more annoyed over the $50 tip she’d lost out on, or the thought that this dirty old man had lecherous designs on her which he thought some cheap leggings would pay for.

Getting back into the truck as the ferry pulled into Tangier I noticed the Mercedes 609 with the German number plates parked next to me. A red faced ruddy man at the wheel. A Descendeur for sure.

“Where are you going with your truck?” I asked.

“Gambia.” He announced proudly, anticipating the usual flicker of amazement that people always give when you announce you are driving deep into Africa.

I declared my credentials. “You stay at Camping Sukuta?” It was the place where all the Germans stayed, despite the owner’s money grubbing best friend that pulled all manner of tricks to get you to sell him your car for a knock-down price. “Say hi to Wolfgang from me, just watch your wallet when he’s around.” His cheeks perked even redder.

In the time it took for the car deck doors to open we chatted about characters along the way, the route through Senegal, the contents of his van, and what a 609 is worth in Gambia these days. I didn’t understand much of what he said, my German is terrible, and he made no effort to simplify his replies.

He glowed with a confident expression I recognised from my time as a Descendeur (Literally “The taker-downers”, it’s French slang for someone who takes cars down to sell in West Africa) and as a tour guide, bordering on smugness, proud to be travelling and making money while he did it. Maybe it was just the glow of the cheap Lidl beers his boozy breath betrayed.

Five thousand Euros his truck would be worth he shrugged with false modesty. In the back, one and a half tonnes of batteries for plant equipment, along with the usual assortment of generators, pumps, spare parts and household electronics, which could be traded for fuel and repairs along the journey.

“And the Moroccan customs?” I asked, weary from my experience when three of us tried to bring in two lorries, four cars, a van, a couple of motorbikes, a Mercedes engine, six radiators, 2 tonnes of biodiesel, and 11 truck tires but got stuck here for a week narrowly avoiding having the lot impounded.

“Alle sind mein Freund” Everyone is my friend. He winked as he rubbed his fingers together feeling imaginary cash.

The mêlée of Customs formalities endures. Arm waving, paperwork, and waiting. While I tried to stand my ground in order of arrivals, I spotted a couple of cars with French plates and Senegalese drivers. In all my years (eight) as a Descendeur I only ever saw one African Descendeur. He was Senegalese too and explained that to combat the overt racism of the Moroccan police he wore a blue velvet jacket and polished shoes.

The ditsy South Carolina belle I was reluctantly guiding pointed him out to me as he spoke with a trio of Belgian men and asked disconcertedly, “Are those Belgians sharing their car with their butler?” It was just one of countless idiotic things she said that eventually prompted me to quit.

The last straw came when she insisted I ask the priest of the church we were in who a statue of a woman holding a baby depicted. She wasn’t convinced when I told her it was the Virgin Mary, and the understandably priest just stared back at me trying to figure out if I was an idiot or a heathen.

Sharing the dumb things clients said kept me and my ex sane. There was the time someone reminded her that Napoleon and Michelangelo were brothers. The difference between Bonaparte and Buonaroti, as well as the small matter of a few hundred years presumably not being so critical in the “olden days”. Another insisted that they had removed the lower third of the Eiffel tower since her previous visit to Paris. But my favourite was the regular request to point out kangaroos when we crossed into Austria.

The Senegalese guys in Tangier were both driving Peugeot 405s. In my days it was 504s. Times change. The Moroccans seemed pretty fair to them, and they were the first out of the gates. They had friends at the Senegalese border post of Diama, who would squirrel their cars in avoiding the fees that the German would have to pay.

My turn eventually came and the forms were filled out, rubber stamped, and after a cursory search I was shown the gate too.

Meanwhile the 609 had been pulled off to the side. While in the past you could rely on the laziness of the customs not to search too deeply in overloaded vehicles, they now unveiled a mobile X-ray truck. Those contraband batteries would show up like gleaming beacons. The Moroccans had come a long way since my Descendeur days and all that Gambian-bound hardware was about to be confiscated 3000km short of its destination.

I glimpsed the German as I pulled out offering up something from his truck to avoid being exposed by the X-rays. I couldn’t see for sure but it might have been a Hershey bar, or a pair of nylons.

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.