The forgotten energy saving potential of the microwave oven (also quick low impact vegan pizza recipe)

The recipe book which came with my
first microwave over in the 1980s

Click these links for the recipe without the story, to find out how much CO2 was emitted, or for how far you can cycle using only the energy in the pizza.

Back in the early 80s I bought a microwave oven for my mother with some of my earnings from my first job. Microwave ovens were not really a new invention but they were not entirely commonplace yet in the UK. I don't think my Mum really wanted a microwave at the time, but she became quite convinced by it and made quite good use of it because it allowed some recipes to be cooked just as well before, but in less time. A year or so afterwards I packed in the dead end job and became a student but my accommodation consisted of one room in a building with no shared kitchen. For several months I ate nothing but salad for my evening meal, which was healthy enough but ultimately not so varied, so I bought a second microwave oven and began to learn to cook with it.

Microwave ready meals were not really a thing in the early 1980s so people didn't buy microwave ovens merely to warm up frozen pizzas. Because many owners had no previous experience with microwave ovens they were supplied with information about how the oven worked, what it was useful for, and complete recipe books. My first microwave oven was a Samsung and it came with this book.

They were both full of tempting looking meals,
completely cooked by microwave

Inside the Samsung book there were a wide range of recipes some of which became favourites during my student days. However this book was of course aimed at every potential buyer so it included a lot of non-vegetarian recipes which were of no use to me so I bought a second book which while not completely vegetarian did include a lot more recipes for things that I wanted to eat.

I ate fairly healthy food when I was a student, and very nearly every evening for a period of years I prepared my meal in the microwave oven, everything cooked from fresh ingredients. The budget was small but the food was good.

Microwave ovens are not the best way of cooking every type of food. Some of my experiments as a student were not total successes. For example, at that time I didn't understand about how bread was made and I once ended up making my lunch sandwiches out of incredibly dense lumps of dough for half a week because I couldn't afford to throw anything away. But microwaves have advantages for some kinds of cooking.

The forgotten potential
My old microwave cookbooks include short descriptions of why microwave cooking is advantageous. For instance, the microwave oven consumes far less energy than a conventional oven to achieve the same result, it saves time and it's less dangerous to use because it doesn't get hot in itself.

Much of the potential seems to have been forgotten with microwave ovens now being seen by many people as useful only to warm up low quality frozen food.

We've done this with our produce. Quick, easy and effective.

There is more awareness now than there was 35 years ago that we really should be trying to consume less energy, but while we now have an image of ourselves as being "green", we actually consume twice as much electricity now as we did back then. The average person was actually more frugal before anyone had LED lighting in their home or solar panels on their roofs.

These books are full of recipes for proper food.

Now, more than ever, we need to address our excessive energy consumption and enormous CO2 emissions. We can start in the kitchen. Switching to a vegan diet is of course enormously beneficial because a plant-based diet produces far lower emissions than does a meat and dairy based diet. But we can go beyond just the savings due to the ingredients we use by changing how we cook.

An online discussion a few days ago revealed how remarkably energy and carbon intensive a pizza can be if it is a frozen pizza, warmed up and delivered to your home. There's no obvious reason why a pizza should be so damaging. It is, after all, basically just tomatoes on toast. However this prompted me to think about one of my favourite dishes when I was a student: microwave quick pizza. This took no time to make and included no exotic ingredients so surely had a low footprint.

Quick low impact inexpensive vegan pizza

I clearly referred to this page quite often
when I was a student.

When I was a student, one of my favourite recipes was a basic microwave pizza. This took less than 15 minutes to cook from scratch, it was very simple, it was tasty and it was nutritious.

The original quick pizza recipe which I used as a student of course used cheese as a topping, but I've been vegan for decades now and so I always substitute something else. There are many commercial cheese substitutes. I've tried most of them in the past, some are better than others and you may well find one that you really like. However we cook from basic ingredients every day so we don't usually have things like "vegan cheese" in our refrigerator. For the pizza which I've made for my lunch today I've used nuts as a substitute for cheese. That may sound a bit, well, nuts, but it's not actually a bad substitute. Nuts contrast with the tomato, they provide protein and oil as does cheese and in any case many commercial vegan "cheeses" are made at least in part of nuts.
Ingredients for the base (makes one pizza)
120 g self rising flour
20 ml olive oil
35-45 ml water
pinch of salt

Ingredients for the topping
100 g tinned tomatoes, drained.
10 g peanuts, crushed.
1/2 small onion.
2 cloves garlic.
Basil, oregano, salt and pepper, nutritional yeast to taste.

Instructions
Mix all the base ingredients together into a dough. Add the water slowly as you want a nice dough and not something too sticky.

Slightly oil a plate and spread the pizza dough on it. It's not a bad idea to make sure that the sides are slightly high to contain the topping, but the topping shouldn't really be wet so this isn't actually very important.

Microwave on full power for about 3 minutes. The pizza base will become puffy and rise slightly.

While the base is in the microwave you have time to drain the tomatoes (if they're too wet then the entire pizza will be too wet), chop them, crush the peanuts in a mortar and pestle and also finely chop the onion and garlic.

When the pizza base is ready, spread the onion and garlic on top and microwave for two more minutes. This softens the onion a bit, which doesn't happen so readily if you put it in with the tomato already on top.

Now add the tomato, herbs and crushed nuts and microwave for another 3-4 minutes.

Add salt, pepper, nutritional yeast to taste.

Perhaps not the best pizza in the world. Perhaps some people wouldn't even consider it to be a "true" pizza. I don't much care. It's tasty, nutritious, quick to prepare from scratch and it's all I've got for lunch today.

I like cabbage, perhaps more than most people, so I added some of that to the topping as well at the same time as the onions and garlic. I also added capers before the last microwave step and I topped it off at the very end with a few small tomatoes from our garden (it's nearly November but we still have the last of the fresh tomatoes) and a few basil leaves also from the garden. You can add anything you like.

Obviously if you're alergic to peanuts you should substitute something else. Nothing is very critical. It will probably also work with gluten free flour.

Note: This isn't a real bread recipe. It's more like a recipe for a scone (you can make good scones in the microwave). The rising action in this case is the result of a chemical reaction with the sodium bicarbonate in the self rising flour. This chemical is all that distinguishes self rising flour from normal flour and you can just add a tiny quantity yourself (its sold as baking powder) to normal flour if you want. Baking with yeast is different. If I had know about that difference when I was a student I wouldn't have had to eat solid bread for a week (see story above).

0.08 kWh consumed in
the 19 minutes it took to
make the pizza, write
down what I was doing
and take all the photos.

A low carbon meal

Having cooked and eaten the pizza we can now calculate the CO2 emissions which resulted from it. The electricity is easy: There are articles online which show the carbon intensity of electricity for different countries. Exact figures vary but for the Netherlands, and across Europe, around 500 g/kWh seems to about average. My plug-in usage meter measured 0.08 kWh used in total by the microwave. Generating that amount of electricity would normally result in about 40 g of CO2 being released. Because I cooked this pizza at lunch-time the microwave oven was actually entirely powered by our own solar panels. The electricity meter span backwards the whole time. But I will stick with the 40 g for this calculation as it's more representative.

Impacts for the ingredients are taken from this link (it refers to Finland, but I can't see most of them would vary much elsewhere).

Ingredient	Quantity (g)	CO2 equivalent (kg/kg)	Total CO2 (g)	kcal
Electricity	0.08 kWh	500 g/Wh	40
Flour	120	0.8	96	400
Olive oil	20	1.5	30	160
Water	40	0.5 (for mineral water. I used tap water)	20
Salt	0	0	0
Tinned tomatoes	100	0.3 (vegetable juice)	30	19
Peanuts	10	2.3 (nuts and almonds)	23	61
Onion	30	0.2	6	12
Garlic	10	0.2	2	3
Cabbage	30	0.3	9	7
Capers	5	0.1	0.5
Herbs, salt, pepper	5	0	0
Total carbon footprint / calories			256.5 g	662

So I've calculated that my lunch had a total impact calculated of around 260 g CO2. I've been a bit unkind to myself because our electricity has a lower impact, at least in the daytime, and my water definitely has a lower impact as it came from the tap - I never buy mineral water so in this case around 200 g was probably more accurate. Either way, the total is small enough to fit into most carbon budgets.

The total weight of the finished pizza was about 370 g (very little liquid had a chance to evaporate, and the rest of the ingredients stayed in the plate). So the impact of a pizza made in this was is 0.7 kg CO2/kg food. This makes sense because it's somewhere in the middle of the impact of the ingredients themselves. It's a very long way removed from the 19 kg/kg figure given at the link for "pizza", but it's clear that what they're referring to is a ready made or delivered meal of some kind.

Another study suggested that a frozen pizza in Norway could have an impact on the climate equivalent to as much as 290 kg CO2. My recipe has less than 1% of that impact.

Conclusion
Following the recipe above you too can make a pizza which is quick to prepare, tasty, nutritious and has about 1/30th of the environmental impact of a delivered pizza. If it had been cooked in a conventional oven then the energy consumption would have been far higher. The energy saving potential of microwave ovens is largely not appreciated, but it should be. We are killing our planet with over-consumption of many things, including energy.


Addendum: What can we do with 662 calories?
662 calories is more than a quarter of the daily requirement for an average man and very close to a third of the recommended daily for an average woman. We need to eat that amount every day just to be healthy. We also need to exercise for about half an hour every day. So let's work out what can be achieved by using those calories.

We should always bear in mind that we need 30 minutes of exercise every day just to maintain a healthy body. In 30 minute we can cover 15 km on a bicycle, so by cycling we effectively get 15 km of travel for free every day with no impact on the environment over that of the food we have to eat anyway.

Velomobiles are the most efficient vehicles on the planet. But can you get a
subsidy to buy one of these ? Of course not. However the Dutch government
will give you €6000 to buy an electric car which produces far more pollution.

However if we ignore that and simply plug the calories that we have into a calculator and work out the potential then we find that with a standard town bike we can ride an impressive 32 km at just over 20 km/h using nothing more than the energy from the pizza. If we use a more efficient type of bicycle then we can cover 46 kms at 30 km/h using just that pizza as fuel. That works out as about 5.65 grams of CO2 emissions per km for the efficient bicycle and about 8 g CO2 per km for a standard bicycle. By comparison, in the Netherlands, an electric car produces about 60 g CO2 per km and a diesel car anywhere about 120 g per km.

A cyclist can easily travel with a tenth of the emissions of the driver of even one of the most efficient cars, but even that comparison is unfair because actually we get our first 15 km for free.

The surprising cost of a pilot light (waakvlam)

We have a low energy bill. This is the case because we've done quite a lot of work in our home to improve the insulation so that our central heating rarely comes on, and we've tackled our electricity consumption by installing solar panels. However, we've not yet done anything to the gas equipment in our home which was already here when we moved in 12 years ago, in part because until now it's not been easy to tell which piece of equipment used most gas so should be targeted first.

While we've had a smart electricity meter for almost a year now, and I've used a plug in measuring device for much longer to check which appliances had higher than expected consumption, our energy company didn't install a smart gas meter until a week ago. The old meter was not easy to read for small levels of usage. But the new meter has made it easy to find out something which I had long wondered about: How much of our not very high gas consumption was wasted to no effect.

The new gas meter. Since installation we've burnt 5.725 cubic metres of gas.

The gas water heater

How much gas does a pilot light (waakvlam) use ?
Our house has three devices which run on gas: The gas hob in the kitchen, the central heating boiler and a separate water heater which heats water only for the shower, bath and bathroom sink.

The water heater is really old. Old enough to use a pilot light (waakvlam) instead of starting itself with an electronic igniter whenever hot water is required.

If you're unfamiliar with what that means, there is a very small flame which burns continuously, 24 hours a day, 365 days a year, just waiting for someone to turn on the hot tap so that it can be used to ignite a much larger flame to heat water.

In the past I've asked several people who work for the gas company, or otherwise seem to know about gas appliances how much gas is used by such a flame and I've always been re-assured that it's "next to nothing", "unmeasurable" or "similar to a mobile phone charger", but I was never quite convinced. The new gas meter has allowed me to measure how much gas is being consumed and the result is surprising.

The pilot light. It's small, but any gas burnt here is wasted.

Meten is Weten. It costs how much ?
One day this week we took readings from the gas meter while avoiding using any gas appliance for 18 and a half hours so that period passed with only the pilot light burning gas. Over 18.5 hours, the meter showed that 0.283 cubic metres had been consumed. That equates to 0.366 cubic metres per day or 134 cubic metres per year.

134 cubic metres of gas isn't insignificant at all ! In fact, it turns out that in summer months our gas usage is dominated by the consumption of the pilot light, which consumes more than we use for hot water and cooking combined. Over the whole year it consumes rather more gas than we use in February to heat our home. It's an appalling waste not only of gas but also of money: That pilot light costs us nearly €90 a year to run.

Like a phone charger ?
The comparison made previously with a mobile phone charger is particularly absurd as phone chargers genuinely do consume an unmeasurably small amount of electricity when they're not in use (unplugging them is something that some people do in an obsessional way because it looks like it'll save energy, when actually the effect is almost nothing at all). But this pilot light consumes a very measurable amount of gas. 134 cubic metres of gas is equivalent to about 1340 kWh of electricity. If a phone charger used that much it would certainly be measurable. It would also add somewhat more than €100 a year to the electricity bill and the charger would be rather hot rather than cold to the touch.

The next step
Obviously this old water heater has to go. That has long been the plan because actually we'd like to get rid of gas altogether. It's not happened yet because we prioritized insulation and electricity first. But discovering how much this thing wastes has given new urgency to the plan. At the very least we need to be rid of this water heater. It appears to be possible to buy an instant electric heater for about the annual cost of the gas for this, and an electric heater would effectively cost nothing to use because it would operate on the excess electricity from our solar panels which we currently export to the grid and for which the electricity company pays us very little. So I expect to change this quite soon.

Update: The pilot light no longer burns!

It took us a few years to get around to it, but we did eventually replace this inefficient water heater, saving both gas and money. Read more about what we replaced the gas heater with and how this change will bring our total future energy bills close to zero.

Seven years of solar power: How valuable is our solar energy ?

I've been interested in solar energy since before I can remember. My first practical experience beyond things like solar powered calculators was in the mid 1980s when I put a square meter of surplus panels on the roof of my parent's home. These provided 12 V DC which I used, amongst other things, to charge the battery in my then quite new laptop computer. It wasn't until seven years ago, though, that we installed a large system on our home and the seventh anniversary of that system passed on April 5th.

Seven year summary
We have 16 panels each rated for 235 W output for a total of a 3760 W peak. In this part of the world it is usual to calculate the expected total output as the equivalent of 925 hours of full sun each year on the panels, giving an predicted output of 3478 kWh per year. In practice, over the last seven years our system produced 23601 kWh in total or an average of 3372 kWh per year.

Output per month over seven years. Red bars show our electricity consumption, blue bars show the production from our panels and the yellow line shows where we are in total now relative to where we began. Our production in is higher than our consumption on average, though obviously that is not the case in the winter. The kink in the yellow line from July 2018 is the period during which our inverter was not working (I repaired it myself)

Several things contribute to the slightly lower output relative to the estimate: Our panels are mounted at the angle of the roof and not at whatever the ideal angle might be, they face South West rather than directly towards the South. But the most damaging thing so far as the average is concerned is that our inverter failed last year and so we had no output at all for a few weeks during the sunnier than average month of July. Calculating out average output for the six years before the inverter problem we come to 3410 kWh per year which is within 2% of the prediction.

Return on investment
The monetary value of the electricity which we've generated is about 20 cents per kWh for that which we use ourselves and about 7 kWh for the excess that we export to the grid. We have exported about 1200 kWh in total for a value of €84 and consumed about 22400 kWh ourselves for which we would otherwise have had to pay about €4500. In total, then, about €4600 has been returned from our original €8000 investment. If the same rate of return continues then the system will have taken 12 years to pay for itself.

Our new smartmeter. When the photo was taken
everything electrical in our home was powered
from the panels and 2 kW was being exported
to the grid.

If the inverter fails again and this time we have to replace it then that will of course increase the repayment time. This might happen. However the panels themselves are expected to last much longer than the repayment period.

A smart meter
Something else which changed last year was that our electricity meter was replaced in December.

The new meter doesn't give us any real advantage over the old mechanical meter which span backwards just as enthusiastically as forwards for nearly seven years. The electricity costs us the same amount either way around.

Of course it does offer an advantage to the electricity company because they no longer have to ask us to read the meter or visit to do so themselves.

What the new meter does give me, though, is that it counts differently and therefore I have a little more information for future calculations. While we pay the same amount of electricity in peak and off peak periods, the meter displays them separately, for both inbound and outbound electricity. So now we can see how much electricity we consume at night time and we can see how much leaves our home rather than being consumed here.

Solar electricity is more valuable than average because it is
generated at peak times of consumption (source)

Perhaps after a year of recording this information I'll have something which which I can create an interesting graph. Thus far I have just three and a half months of this extra data, all of it from winter and spring. There's not much contrast to see.

What has long been obvious of course, and is also visible even in the small amount of data which I have now, is that our electricity is generated only in the daytime and then mostly on sunnier days. As it happens, solar electricity remains quite valuable in the Netherlands because this daytime generation corresponds reasonably well with peak usage. That means that the electricity which we export, most of what we generate, is almost certainly of use to someone else.

The first thing I made the prototype
hardware do was wiggle a GPIO and
then send serial data as shown here.

Software for a smart meter
I'm late to have a smart meter installed but as it happens, I spent a few months two years ago working on software for the prototype smart meter hardware of one of several competing manufacturers. I'm almost certain that the meter that I have now is not related to the manufacturer for whom I did the work, so my code is almost certainly not involved in reporting my own electricity usage, but as I'll never open the box of the meter and look inside, I'll never know for certain.

It was quite an interesting project for a while because it was like a return to the old days for me, when I worked on 8 bit processors and embedded software. This work was with what for me was a new processor, the Renesas RL78. It's a quirky 8/16 bit design. The RL78 assembler is styled so that the source code looks a bit like that for the Z80, but the processor is really completely different. In total I had 32 kB of flash and 4 kB of RAM to work with. These days that doesn't sound like much at all but that means this device has about the same amount of memory as the guidance computers which took Apollo to the moon so it's enough to do great things. In this case it's in a finger nail sized package which consumes micro-watts, and the little RL78 can of course compute many times faster than the AGC.

Power for a home and a business
We generate more than enough electricity to power both our home and our business, though of course I always point out that we're not actually doing so at night, or on darker days in the winter. Anyway, if you want a support a solar powered bicycle business which uses no powered vehicles then you can do so here: