How the environmental footprint calculator works - please give input

21

Hi Tom,

Some thoughts on the food section.

There seems to be an error in the logic on the %meat in diet. If I have 20% of meals with meat, I would expect a lower footprint than e.g. 80% meat. Have you reversed the logical order you intended?

Basing the diet on £spend/week I think gives a false view of the carbon footprint of the food. We may elect to buy a more expensive chicken (free range organic vs. standard) or a £20 bottle of wine rather than £5 for a range of reasons, but the impact on the carbon footprint is not simply a scaling of the cost of the chicken or bottle of wine.

In fact we should only eat the number of calories to sustain our body weight and fitness/exercise level. So it would be more appropriate to scale the diet by calories than amount spent.

Of course, the problem with this approach is that we all tend to under-estimate how many calories we consume! But at least there are government guidelines we can follow.

I undertook a project to keep a 28 day diet diary of all food ingredients in my diet (which is one day on, one day off meat - thus giving me two 14-day period of meat and vegetarian diets).

I then analysed the carbon footprint of the ingredients using the Poore & Nemecek paper (which is used by the Our World in Data study) together with a more extensive meta-study by Clune et al. “Systematic review of GHG emissions from different fresh food categories”, Stephen Clune, Enda Crossin, Karli Verghese, Journal of Cleaner Production 140 (2017) 766-783 and data from Tesco, Coca-Cola, the EPD programme (Environmental Product Declaration) and Booths Supermarkets (studies by Mike Berners-Lee of Small World Consulting). The issue with the Poore & Nemecek meta-study is that it is a “world average” not UK-centric. By including data from the other sources I was able to build a more “UK-centric” view of the global warming potential of the different foodstuffs.

I also categorised the foods into sub-categories (Dairy, Beef/Lamb/Pork, Poultry, Eggs, Fish, Whole Grains, Starchy Veg, Vegetables, Fruit, Legumes/Pulses, Nuts, Oils, Sugars/Sweets/Snacks, Alcoholic Drinks, Soft Drinks) to more easily compare with other studies on carbon footprint of food. These categories reasonably aligned with the .gov “Family Food Trends” data you cite.

As well as the GWP (CO2e/kg) of each food item, I also included the kcal/100g and protein/100g - so that I could check I was getting my required daily calories and RDA of protein.

And finally I created a “typical” diet based on the nation’s favourite foods (e.g. ceareal for breakfast, sandwich lunches, spaghetti bolognese etc. for dinner). My diet has 2,900 kcal and 100g protein (I am active and do triathlons). The typical diet was also 2,900 kcal for comparison. I have scaled the data back to 2,500 kcal (RDA for man) to give the following output:

2500 kcal GWP of diet kgCO2e/y High meat-eaters 1880 +17% Medium meat-eaters 1595 - baseline Low meat-eaters 1010 -36% Vegetarians 860 -46% Vegans 665 -58% Planetary Diet 897 -44%

Not a million miles off the numbers you have for the “average spend” of £40-50/week, but lower. Clearly if you scale by calories, this will fall further still for a woman (2,000 kcal/day) and rise for fit and active men (like me at 2,900 kcal). It scales linearly. If you scale by £/week then you can double or treble the carbon footprint or more, which I don’t think stacks up against the data. Sure if you buy more “exotic” ingredients, this will likley increase the carbon footprint, but not by three times. The “where do you get your food from” question could be used to provide a scaling vs. “climate consciousness” of shopping, with a factor of >1 for “don’t care where the food comes from” to account for large amounts of exotics and bottles of expesnive wine shiped from Chile etc. (probably around 1.25 as a factor).

The difference between my medium meat (meat every day but not every meal) and vegan is -58%, which aligns with your factor (0.43). However, I have a bigger impact of vegetarian (0.56 vs. your 0.81). Low meat (every other day) comes in at 0.64 as compared with your 0.85 (?). I think reducing meat % has a bigger impact than you are accounting. I have developed a spreadsheet which could model different diet choices, whcih you could play with if you were inclined.

One thing that came out was that the “typical” diet I constructed, which was high meat, was also high in protein - 120g/day - almost twice the RDA. Our bodies only need a certain amount of protein, so over-eating meat is wasted protein. Reducing the meat proportion of the diet is not only good for the planet but means also that we are not wasting protein resources.

You will also note the reference to the Planetary Diet. A Lancet Commission published a report on “Healthy Diets From Sustainable Food Systems”, EAT-Lancet Commission (https://eatforum.org/eat-lancet-commission/eat-lancet-commission-summary-report/). This made recommendations for a healthy diet mix that was sustainable for the planet. They allow a small amount of meat and fish to be eaten, de-emphasise whole grains and increase the amount of calories from nuts and pulses. For the 2,500kcal diet this is around 1,000 kgCO2e.

I think there should be a greater penalty for food waste. I think you have looked at the impact of disposing of the waste only. In fact it should directly impact your footprint, as you are buying the calories but not eating them. So 20% waste means that your carbon footprint increases by 20% as you still have that impact of buying the wasted food. This means that the quick win is to reduce what we buy and eat what we cook and throw away the minimum (5% realistic). WRAP reckons that we waste 22% of what we buy on average: https://www.wrap.org.uk/sites/files/wrap/Household_food_and_drink_waste_in_the_UK_-_report.pdf

Hope this helps, happy to disucss further. Alex

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22

Not sure if I have missed the point here. If you already know the kWh use in a house (from the energy bills) then you don’t need to do any calculation to estimate how much electrical energy is needed to provide heat to the house. You already know the kWh.

If you want to consider moving from gas heating to a heat pump, that is when you need to do a calculation. It is not part of the starting carbon footprint calculation (if you already have aheat pump then your energy bills will already give the kWh|).

Sorry if I have misunderstood you.

Alex

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23

House leakiness is not really something you can guess. It is possible to test for it - see for instance the CHEESE program in Bristol: https://cheeseproject.co.uk/ where they come and do thermal and draft surveys of houses.

EST gave some estimates of savings from attending to draghts around doors and up chimneys (which you have used),. You will probably know if you have a leaky house as you will feel the temperature difference (our bodies are sensitive to 2 degress difference between head and feet). So even if you whack up the heating if it is draughty you will still “feel” cold.

As I said, much of our housing stock is in higher EPC category (double glazed and good fitting doors) so the opportunity to reduce draughts is minimal. In an old draughty house, draughts are the second thing to address after the loft insulation. I think my point is you will need to ask something about the age and build of the house and whether it “feels cold” (i.e. draughty) and then for those people give them a large number (10-20%) potential saving. For those with more modern houses or who have already fitted double glazing and new doors, the saving is going to be minimal (all houses except Passivhaus need ventilation to breathe).

I recommend a read of this article to help put it in perspective: https://www.carboncommentary.com/blog/2014/01/08/reducing-draughts-a-national-competition-to-show-how-much-can-be-saved

And in terms of how to model potential savings from fabric changes, you can’t really avoid doing a SAP type calculation based on the current fabric of the house (the U-values of the various elements). EPCs use a “reduced SAP” calculation RdSAP for instance, which is how they calculate 1) the current energy performance of your house (compared to a model house) and 2) how making changes like double glazing, floor insulation etc. will impact the EPC. Sadly you need to be a registered EPC assessor to access the tools (e.g. https://www.stroma.com/software/fsap).

The CE54 heat sizing tool from EST uses the SAP model in a simple way, so that may give you a way forward. I have emailed the spreadsheet to you, so you can see how the calculations are done. Essentially the fabric of your house is in pull-down menus (so you can choose for instance when the house was built and if it has double glazing - the former influences the U value of the walls and the latter the U value of the windows). Then, based on the house size you get a heat loss calculation. Then as you make changes you can see the impact. I expect that you can make your own model based on the CE54 with some simple questions. The number of fabric questions is relatively limited, as are the questions about number and size of rooms. The U-values by the way are also in the EST report I shared “Review of potential for carbon savings from residential energy efficiency”.

EST have another tool that seems to be based on the same kind of data (Home Energy Check). Sadly you cannot see how the calculation is done but it does give you a clear idea of the range of questions and the kind of choice you have (you could play around with the house selection in this tool and see what choices get openend up if you e.g have a pre-1950 house as compared to a post 2000 house). https://homeenergyscotland-advice.est.org.uk/ Give it a go.

You will note that they only talk about leaky doors and give an estimate of how much energy you could save (not asking the question as to whether you have already fixed leaky doors). They also seem to assume you won’t have LED lights as well, and give that as a potential saving.

Maybe when you have surfaced from your other activities, we should have a chat about how to model all this.

Alex

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24

Thanks Alex. I really like the idea of asking simple questions in this area around diet to determine consumption, without directly asking about calorie intake (although we could provide an estimation then allow the user to correct it).

Questions about gender, activity and weight, should probably do it but could be off putting. Anyone else have an opinion on this?

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Try this simple calculator (methodology given) - will calculate the calories required based on age, weight and excercise level. https://www.calculator.net/calorie-calculator.html

26

Hi Tom,

Today I will focus on transport.

Whilst you have used the .gov data (you state DEFRA but it is now BEIS who publish this - the link is correct) for company reporting for trains, planes and buses I was wondering why you had not used the same figures for cars?

I appreciate you want to include the embodied energy in the car manufacture as well as driving the car and fuel use. The Ricardo report talks about a “typical” car with an embodied energy of 5.8tCO2e. This agrees well with another report from Carbon Trust: https://prod-drupal-files.storage.googleapis.com/documents/resource/public/International%20Carbon%20Flows%20-%20Automotive%20-%20REPORT.pdf

However, this is a typical car. So it would be fairer to ask a question about car type & age and scale the embodied emissions according to the cost/RRP of the car. The .gov figures give a range of car types and gCO2e/km driven so you can easily attribute an RRP against each type and then scale the embodied energy. A typical car cost is £28,000 - so a super-mini at half this price would have half the embodied carbon and an Executive car at twice this would have twice the embodied energy. Agree that the data suggests a further uplift of 20% for a PHEV/HEV and 50% for BEV.

You meed a question about age as well, becasue if the car is >12 years old then you can say you have paid off the carbon by then (i.e. the embodied carbon is split equally over 12 years and then zero thereafter).

My calcs suggest for a supermini doing 10,000 personal miles a year the CO2 footprint is 2,501 for mileage and 321 for embodied energy, totalling 2,822 kgCO2e/year. For an Executive car this is 3,808 and 1,071 = 4,879 kgCO2e/year.

In the case of PHEV and BEV there is a supplementary question of where you charge the car. If 100% is at home then you have already captured the carbon in the home energy kWh question. It may be fair to assume a % is charged on the charging network (e.g. 30%) and so the carbon footprint of this uses the facor in the .gov table for BEV. So for example a small BEV with 70% charged at home get 650 kgCO2e for mileage and 1,125 kgCO2e for embodied eneryg per year totalling 1,775kgCO2e (so still better than the IC engine small car).

A medium (250cc) motorbike comes up as 1,656 mileage and 64 embodied = 1,720 kgCO2e/year.

On planes whilst I appreciate that hours flying is a short way of asking the question, there are considerable differences in whether this is short-haul (e.g. domestic or EU) or long-haul or ultra-long haul. The choice of class makes a mssive difference as well. The .gov data has all this covered, and can be asked in some fairly simple questions to get a better view of the carbon impact of your flight choices. For instance one easy choice is, if you HAVE to travel by air, is to travel ecomony not business class - or travel once every 5 years for a special holiday not every year.

The other issue with flying is radiative forcing (the increased impact of the emissions at altitude). A subject of some debate within the IPCC and academia. The .gov data quotes gCO2e/passenger.km without RF and with RF of 1.89. I think this is an optimistic view of the RF effect and a factor of 2 (short haul) and 3 (long-haul - higher altitude for longer) should be used which better aligns with the IPCC view.

So, for instance, 10 flights of 1 hour each way is ~250miles each way in the UK, round trip = 5,000 miles total. In economy gives a footprint of 2,171 kgCO2e (one class in the UK).

1 flight of 10 hours each way is ~ 5,000 miles international flight = 10,000 miles total. In economy ths gives 3,825 kgCO2e and in business this gives 11,094 kgCO2e.

So 10 hours of flying gives very different answers depending on the route and class.

Need to check that the answer is personal use not business flights, as businsses have to seaprately report their carbon footprint and this is a personal footprint calculator (same applies to mileage in cars, trains etc.).

Hope this helps, more another day!

Alex

27

Hi Tom,

Today I will focus on “things”.

This is (naturally!) another difficult area to pin down in the detail. However, we can say what the total carbon footprint attributable to our consumption of all goods and services should be. This is in the DEFRA report UK’s carbon footprint 1997-2017 https://www.gov.uk/government/statistics/uks-carbon-footprint

Per head of population we are at around 11.0 tCO2e/year. And the majority of this is due to our consumption of goods and services in their broadest sense - so not only clothes, shoes, hotels but also mortgages, investments, insurance etc. etc. All of this has a carbon footprint.

The DEFRA data is subdivided in their excel spreadsheet into SIC codes (standard international reporting codes for industrial categories), so it is potentially possible to square the carbon footprint from these broad areas to actual goods and services. They also usefully split out the carbon emissions due to local and national government spending (e.g. hopsitals, refuse collection etc.). The total per head of poulation (including kids) is just about 1tCO2e/year. So we ALL have this and can’t do much about it by our choices. But this valeu needs to be shown in the carbon calculator.

So this leaves 10t/person/year that is attributable to our spending. Some of this is already accounted for in the previous questions (home energy, transport, food). It is possible to filter the DEFRA SIC codes to remove these categories and that leaves an emissions figure that, per head, comes to around 4.8tCO2e/year.

Other research strongly indicates that our carbon footprint is directly linked to our household disposible income. Hence it is fair to say that the 4.8t/person/year should be apportioned by the total HH disposible income and its population distribution rather than equally divided between all people. This also means that we can make choices to reduce our footprint in the tool by deciding what to spend our money on. Recall that even saving money has a footprint!

The other data set available is from ONS into our typical weekly spending habits per household: https://www.ons.gov.uk/peoplepopulationandcommunity/personalandhouseholdfinances/expenditure/bulletins/familyspendingintheuk/april2018tomarch2019

This is split into very fine detail, but there are also sub-category roll-ups (e.g. food and non-alcoholic drinks, clothing & footwear, recreation & culture etc.), so we know on average what people spend in each catoegory area.

With a damp towel around the forehead it is possible to mash together the DEFRA SIC codes and the ONS sub-categories to arrive at a kgCO2e/£ spend in each category. So for instance mortgages are 0.44kgCO2e/£ spend and gym 0.39kgCO2e/£ spend. However, asking people to sub-divide their HH spend into maybe 40 categories is a big ask, even though it may give more potential to see the impact of spend in each category.

It may simply be netter to use total HH disposible income. Using further ONS data on HH income https://www.ons.gov.uk/peoplepopulationandcommunity/personalandhouseholdfinances/incomeandwealth/bulletins/householddisposableincomeandinequality/financialyearending2019

The total residual “consumption carbon footprint” (317.8 GtCO2e) (removing the energy, transport and food elements) can then be apportioned fairly by HH disposible income.

For the mean HH income of £35,000 the carbon footprint comes out as 8.37t (the household having 2.38 persons, hence the per capita being 3.5tCO2e/year). If the HH mean income is twice this (£70,000) then the footprint comes to 19.55 or 8.21tCO2e/head/year. More than twice as there are fewer people in the £70k HH income category.

So the main issue I have is that the limited range of choices in the Better Century tool means that the “things” carbon footprint is way too low. In fact our spending on things is the biggest proportion of the personal carbon footprint.

The way I was thinking for my work was to have this total spending footprint and then give examples of how choices make a difference. So I did exactly as you did for clothes, which can be a significant proportion of the footprint ~5%, allowing changes to the materials of the clothing as well as the number of items (e.g. using recycled polyester rather than virgin, wood instead of polyester etc.). Another example was use of mobiel data and wifi data - estimated that data centres account for up to 10% of global electricity demand - so wise use of data is important. But getting your daily news electronically is still lower carbon than a physical newspaper…

In summary, I have modelled a typical household with 2 adults, 1 child, £35k income, 2 cars (both driving 7200miles/year), one flight a year to Spain for a holiday, average gas and elec consumption (12,000 kWh nd 3,100 kWh respectively), a pet dog, eating RDA allowance of calories and wasting 20% of their food. This produces a carbon footprint of the household of 30.2 tCO2e/year or 10.1t per head. Made up as follows:

                    kgCO2e

Home Energy 3094 Transport 7043 Food 7284 Goods & Services 8366 Government 3100

I believe this to be consistent with the .gov (DEFRA) data. My suggestion is that if the Better Century tool does not come close to these figures modelling the same average behaviours, then it will give a false impression. At the moment, I believe that the BC tool is significantly under-estimating the carbon footprint.

Hope this helps, as ever ready to disucss and debate!

Alex

28

Hi Alex,

It’s a good point about cars and we could easily describe them as in the conversion factors. I suppose I simply went on the gCO2 per km factor which puts cars into the vehicle exercise duty tax bands.

I completely agree on the embodied carbon as well - that was lazy. Perhaps you could suggest some embodied carbon figures we use for each of the car types?

The age of vehicles also could be factored but we would run into complications of using conversion factors for old cars.

I’ll also have a think on the source of charging, with the technological capacity of the next calculator. I had difficult with the last in regard to creating questions which appeared due to others being answered - the next one may facilitate this which will make questions like this entirely practical.

I think doing something more complex with air travel is certainly consideration. It would be better if these were additional questions made as a result of another stimulating it. I think also including the radiative forces would be good as well - very good point.

Will come to your next piece tomorrow- now for more website writing.

As always your help to me and everyone is much appreciated!

Tom

29

Hi Tom, the problem with REGOs is that not everything that is labelled “green” is as green as it sounds. REGOs have been trading at 35p/MWh for some time now. They way the rules work is that Ofgem want to see annually that 100% of power on a so-called “green” tariff is backed by REGOs. So a supplier can buy normal (brown) electricity on the power market throughout the year and then simply buy sufficient REGOs on the REGO market to match the power consumed by its customers. So this would typically cost only £1.08 to “green-wash” the power.

Recall that we are ALL, whatever tariff we are on, paying for renewable energy through our bills. About 25% of our unit cost/kWh is paying for the support mechanisms that government has used to encourage new-build renewable generation (Renewable Obligation, Feed-In Tariff and now the Contract for Difference). So in a year, on average, we are paying £125 towards supporting renewables in any case. The government has committed to £9bn/year support up to 2024 for low carbon generation under the Levy Control Framework, this is the total cost of ROCs, FITs and CfD - all of which is clawed back through our bills. So we are all doing a great deal already to support new green generation.

So I don’t think a “green-wash” REGO-backed “green” tariff is adding anything to the picture. Sure the fact that the generator can sell the REGOs helps their business case at little, but the primary income source for a generator has been the subsidy (now only available to large offshore wind farms or very large solar farms and bio plants) and PPA (power purchase agreement) revenues.

Even Ofgem agree that “REGOs do not provide a meaningful amount of support for renewable generation, as the costs are ‘immaterial’” (from the Ofgem Guidance).

So, sorry, we need to look deeper into what the supply company offering the green energy is doing.

Your supplier can fall into the following categories:

  1. Generates 100% of its customer’s power from its own assets (e.g. Green Energy and maybe now Scottish Power with their new Renewable tariff)
  2. Generates a proporiton of its energy from own renewable generator assets and buys direct from renewable generators under a PPA and buys the REGO with the power. (e.g. Good Energy, Ecotricity, Octopus Energy)
  3. Buys all its power under PPAs with renewable generators, buying the REGO with the power (e.g. OutfoxThe Market, Bulb, Engie)
  4. Buys the power at the cheapest possible price in the market (brown energy), buys the REGOs separately to create a green tariff (many hundreds of offers!)

So, maybe you can consider that any company in the first three categories is going beyond “green-wash”. In fact Ofgem have recognised that three companies are building new assets themselves and therefore are exempt from the price cap (thus allowing them to charge more for their power than the cap, in order to fund new generation): Ecotricity, Good Energy and Green Energy.

Ofgem looked at the following criteria:https://www.energylivenews.com/2019/08/01/ofgem-confirms-permanent-energy-price-cap-exemptions-for-three-green-suppliers/

  • By consumers being on the tariff, support is given to generation and production of renewable energy to an extent that is materially greater than that which is brought about as result of subsidies, obligations or other mandatory mechanisms
  • The cost to the licensee of supplying electricity/gas by virtue of the tariff is materially greater than the level of the default tariff cap for reasons that are directly attributable to the support that the tariff provides to renewable energy.

So here, you are materially making a difference by your choice of supplier.

I am not convinced that this is the end of the story, however. Because unless you balance the demand with the supply you will have to rely on brown energy to meet the demand. Wind and solar are variable sources and there will be times in the night when there is insufficient wind to meet the demand of customers on renewable tariffs. What can a supplier do? Well, there is hydro, but that is also in limited supply. There is also bio-gas powered generation (anaerobic digestion). Good Energy and Octopus Energy demand-match their purchasing to their customer’s demand by buying wind, solar, bio-energy and hydro - thus trying to match green energy to demand 24/7.

Ecotricity by contrast, cannot do this. Their “vegan” product means that they avoid any animal waste which is what feeds the bio-digesters - they can only buy wind, solar and limited hydro. This means that even Ecotricity will have to buy brown power to meed demand on occasions and buy the REGOs separately.

So you can see that the picture is far from easy and is not as easy as saying “are you on a renewable tariff?”.

The ONLY way to be certain you are reducing your carbon footprint with renewable energy is to be directly connected to a generator: your own solar PV, wind turbine or mini-hydro scheme.

There are new ways (via smart metering) to be effectively connected to a local generator (on the same sub-station voltage as you) so that energy generated can be directly matched to your consumption (Octopus Energy are offering such a scheme). This would be a direct carbon footprint reduction.

When you buy from the grid, it is much harder to argue that you are individually reducing your carbon footprint through selecting a renewable tariff. Maybe we can argue that companies that source 100% of their energy from renewable generation and demand match (like Good Energy and Octopus Energy) are as good as you can get under the current system. The other suppliers who own generators and buy PPAs and REGOs together are the next best. But any that purely “green-wash” are not really helping the grid decarbonise. So it will be a question of asking which supplier/tariff are you on and doing the backgroudn research into whether the supplier meets the criteria.

This article by Good Energy is a good summary: https://www.goodenergy.co.uk/blog/2019/08/01/it-s-a-fact-choosing-good-energy-genuinely-supports-the-fight-against-the-climate-crisis/

Hope this helps,

Alex

30

Have emailed some suggested embodied carbon figures.

31

Hi Tom,

Suggested data for vehicles attached.

Kind regards,

Alex

(Attachment Suggested Vehicle Data for Carbon Footprint Better Century.xlsx is missing)Suggested Vehicle Data for Carbon Footprint Better Century.pdf (431.9 KB)

32

Thanks Alex. I’ll give this the proper consideration it deserves when creating the next calculator and may come back with a few more questions!

I’ve learnt something new about REGO certificates - thank you!

33

A had a look at the SIC codes and downloaded the spread sheet. There’s a lot to digest there. I will think about how we can embed this.

One of the things I think we’re really missing in terms of impact is the use of data and the carbon impact of that estimated at 1/2-1 tonne of CO2 per person - we should really include that in the questions as well!

With thanks!

Tom

34

I have done some work on this and created a little calculator for carbon footprint of data. Will share this when I get a moment. However, this still forms part of the overall purchase of “goods and services” which is a large proportion of our carbon footprint.

So if you have a separate calc e.g. for data or clothes, then I think that these should be part of the pledges area (with indicative impact of a change in behaviour) rather than part of the main calc. Otherwise you will need to calc a large number of consumer categories in detail, which is nigh on impossible.

Cheers, Alex

35

Agreed. Would be great to see the calculator so can have a think :thinking:

36

Hi Tom, WWF published their own report in March highlighting the role of imported consumption emissions.

What WWF has done, along with Leeds Sustainability Research Institute, is to re-categorise and analyse carbon emissions by industrial sector. Leeds also carried out this work for DEFRA in calculating DEFRA’s consumption emissions totals in their report “UK Carbon Footprint 1997-2016” - so it should not be too surprising that the two reports are largely in agreement. WWF/Leeds have extended the analysis back to 1990.

However, one useful thing in the WWF report is that there is a table (Appendix IV) showing the % contribution to the carbon footprint of each of the 108 industrial categories. This might be useful in creating a tool…

The whole report is worth a read and it back up my conclusion that any useful carbon footprint tool MUST include our imported consumption emissions.

Cheers,

Alex