Our household took our turn with the Transition Leicester Apple Press last weekend, and after a busy and fun day of activity we ended up with litres and litres of bottles of delicious apple juice to see us through the year ahead. Being a carbon nerd, I also seized the chance to work out the carbon emissions associated with each litre of juice we made, which led to some fascinating and surprising results. This post takes you through the process of making our juice, what the emissions came out as, and how they compare to alternatives to home-made juice.
Making our juice
So here’s the apple juice making process in short…
First, we picked lots and lots of apples (5 or 6 boxloads), which we scrumped from a disused allotment site in Leicester.
We picked up the Apple Press from its most recent port of call and took it over to a friend’s house in Sileby where they had a good spacious kitchen and garden for us to do the crushing and pressing.
Preparation involved two steps – quickly washing the apples (picture a sink full of water and bobbing apples) and chopping off any bad bits, and sterilising our juice bottles (glass bottles with jam jar style lids) in the oven for an hour on a low heat.
Step one of the processing was noisy and fun – putting a big bowl full of apples at a time through the drill-powered crusher (where a rotating wooden cylinder crushes up whole apples into nice small pieces).
After emerging from the crusher, we’d have a bowl full of mushed up apples…
… and this apple mush would go into a “cheese” – one of the permeable bags in the press that the juice will seep out through…
Once we had about 5 cheeses stacked up in the press, it was time to squash them! We started off by just pushing down on the press, and then to really get the juice flowing we used the car jack that came with the press to really squash every bit of liquid out of our apples…
We then took the bowls of juice we got out of each pressing and poured them into our still-warm sterilised bottles (we poured a bit into a jug to drink straight away too…).
The bottles were then all put into our pasteuriser (like a small tea urn), where after 25 minutes at 85 degrees, the juice should keep for more than a year. After taking out the pasteurised bottles, and repeating the whole process a couple more times, we had lots of bottles of juice to show for our efforts.
And I should add that it tasted incredible! The nicest apple juice I’ve ever had, and all the more special because we made it ourselves!
Working out our carbon emissions
Before the bottles were even cold, I found myself hard at work with a pen and paper working out the carbon footprint of our juicing! The really nice thing about doing this is that there’s a good benchmark to compare to – Innocent Smoothies are one of the only companies to have had their whole supply chain audited to estimate the carbon footprint of their products. The big question was… would we work out better than Innocent?
I’ll skip all the details of the sums (though the main assumptions are at the foot of this post for the nerdy-minded), but each element of energy use that we counted, and the associated CO2 emissions per litre are shown below…
Driving in car (to move press to Sileby): 4.67kg ; 144g per litre
Driving in car (to collect press): 0.83kg; 25g per litre
Driving in car (to pick apples): 1.67kg; 52g per litre
Crushing apples (with electric drill): 0.1kg; 3g per litre
Sterilising bottles (gas-fired oven): 1.5kg; 46g per litre
Pasteurising bottles: 1.25kg; 38g per litre
Washing apples and washing up: 0.4kg; 12g per litre
Washing cheese cloths: 0.5kg: 15g per litre
That’s a total of 320g per litre so far. Added to that are the emissions for making the press. Our press-maker Rupert actually quantified all the energy used during the process, which came to 7.2kWh. Assuming that all came from electricity, that gives us 3.6kg CO2, and apportioning that between 30 households using the press (using the conservative assumption that it’s used for just 3 years) gives 0.04kg per household’s pressing. In our case, this translates to 12g per litre.
So, in total for our household’s juicing this year, all the emissions that we could count came to 347g of CO2 per litre. It was fascinating to see that car journeys were the biggest part of the carbon footprint. If we hadn’t driven out to our friends’ place to do the pressing that figure would be down to 203g of CO2 per litre. If we could have collected the apples and press by bike trailer instead of by car, we’d be down to 126g CO2 per litre. A home with zero-carbon energy sources could do the whole process with no emissions at all.
We compared that to the results from Innocent Smoothies, who had their whole supply chains audited by the Carbon Trust a couple of years ago. They use a bunch of different fruits (including apples) to make their smoothies, but it seemed like a reasonable comparison to make.
Innocent had an average of about 270 g CO2 per litre for their 1litre tetrapaks in 2007, which they’d got down to around 210g CO2 by late 2008 (see http://www.innocentdrinks.co.uk/us/ethics/resource_efficient/our_carbon_footprint/).
So our particular pressing turned out to be worse than for an Innocent smoothie!
But, having said that, I think there are two important points to keep in mind… for one, our emissions were higher than they could have been because we drove out to a friend’s house to do the pressing (if it wasn’t for that, they would have been lower than the emissions for Innocent). But more importantly, we got to have a really special day, and we’ve taken the first steps towards a way of getting our fruit juice that can be genuinely zero-carbon and sustainable over the long run (once we have zero-carbon energy supplying our homes)… I can’t wait ’til we do it again next year!
Some background assumptions: we did 2.5 pressings during the day, and made 13 litres of juice from each. To convert gas and electricity use into kg of CO2, we divided kWh of energy by 2 (for electricity) and by 5 (for gas). To convert km of driving to kg of CO2 we divided the distance travelled by 6. We estimated our washing up energy use by assuming that we were heating 5 litres of water by 30 degrees with a 90% efficient boiler. We assumed that an oven on a low temperature for an hour will use 1.2kWh. One cycle of the washing machine (to wash cloths) at 40 degrees was assumed to use 1kWh of electricity.