Embodied energy
Embodied energy[1] on Mars is the measure of all the energy required for the preparation of products or services. It allows for a useful comparison of various materials that can be produced in-situ for the construction of martian settlements. The following table is cradle to gate: From mining to production to a finished product at the gate of the plant. A martian settlement will also use operational energy, for moving, heating and cooling the products. Most food product information does not include the solar energy required for growth but only the energy required for food production, fertilisation and transformation. Recycling and energy recovery can reduce embodied energy significantly.
In common materials (from Wikipedia, partially adapted to Mars)
Selected data from the Inventory of Carbon and Energy ('ICE') prepared by the University of Bath (UK)
| Material | Energy MJ/kg | Density kg /m3 | Mars notes | Source |
|---|---|---|---|---|
| Water | 0,5 | 1000 | Melting or condensing from atmosphere | ML |
| Compressed Regolith Blocks (CRB) | 0,5 | 2000 | 5% cement | ML |
| Hydrogen | 180 | Electrolysis of water, 80% efficiency, this also produces large amounts of Oxygen | ML | |
| CO2 | 4 | 1 | Work of compression and liquefaction | ML |
| Propellant (CH4) | 127 | This includes the energy to produce the corresponding Oxygen, atmospheric compression and hydrogen electrolysis. | ML | |
| Food | 1580 | 900-1000 | This also includes biomass, needs to be refined | ML |
| Solar cells[2] | 2088 | Silicon cells, not installed. | ||
| Aggregate | 0.083 | 2240 | This is the energy required to crush and sort the aggregate that is used for concrete production or road building | |
| Concrete (1:1.5:3) | 1.11-2 | 2400 | This is for M20 concrete, slightly better than average concrete | |
| Bricks (common) | 3 | 1700 | ||
| Concrete block (Medium density) | 0.67 | 1450 | ||
| Aerated block | 3.5 | 750 | ||
| Limestone block | 0.85 | 2180 | ||
| Cement mortar (1:3) | 1.33 | Cement with sand mixed in | ||
| Steel (general, av. recycled content) | 35 new
20 recycled |
7800 | From Iron, mining and foundry included, as a finished product. Recycled value is about 60% recycled. | |
| Stainless steel | 56.7 | 7850 | From Iron, Meteoritic iron might require much less energy. Type 304. | |
| Nickel | 165 | 8908 | ||
| Timber (general, excludes sequestration) | 8.5 | 480–720 | Unlikely, at first. Bamboo glued structural elements might provide similar services | |
| Glue laminated timber | 12 | |||
| Cellulose insulation (loose fill) | 0.94–3.3+300 | 43 | ||
| Glass fibre insulation (glass wool) | 28 | 12 | ||
| Rockwool (slab) | 16.8 | 24 | ||
| Expanded Polystyrene insulation | 88.6 | 15–30 | ||
| Polyurethane insulation (rigid foam) | 101.5 | 30 | ||
| Straw bale | 0.91 | 100–110 | Probably much more expensive on Mars, depends on the value of biomass | |
| Mineral fibre roofing tile | 37 | 1850 | ||
| Clay tile | 6.5 | 1900 | Clay deposits are available | |
| Aluminium (general & incl 33% recycled) | 155-220 | 2700 | Alumina is common, but perhaps not in concentrated ores | |
| Medium-density fibreboard | 11 | 680–760 | ||
| Plywood | 15 | 540–700 | ||
| Plasterboard | 6.75 | 800 | ||
| Gypsum plaster | 1.8 | 1120 | ||
| Glass | 15 | 2500 | Primary glass production. Toughened glass reaches 23 MJ/kg | |
| PVC (general) | 77.2 | 1380 | ||
| Vinyl flooring | 65.64 | 1200 | ||
| Terrazzo tiles | 1.4 | 1750 | ||
| Ceramic tiles | 10-12 | 2000 | ||
| Wood | 1200-1500 | 600-800 | Similar to food | ML |
| Wool carpet | 106 | Sheep on Mars? | ||
| Wallpaper | 36.4 | |||
| Vitrified clay pipe (DN 500) | 7.9 | Might be interesting for many uses | ||
| Copper (average incl. 37% recycled) | 42-140 | 8600 | ||
| Lead (incl 61% recycled) | 25.21 | 11340 | ||
| Ceramic sanitary ware | 29 | |||
| Paint - Water-borne | 59 | |||
| Paint - Solvent-borne | 97 | |||
| Carbon fiber composite[3] | 800 | 1800-2000 |
Plastics, for example, have a high value of embodied energy and therefore are not the best choices for construction materials, of other choices are available. Note, energy in plastic feedstock doesn not seem to be included. So on Mars you need to add the energy required to produce the feedstock, probably methane and CO2.
Aluminium requires much more energy than Steel or iron and therefore is less likely to be used for construction on Mars.
The values for wood products and other biological products in the above table do not include embodied solar energy.
With embodied solar energy:
Food: At an average yield of 3 tonnes per hectare (conservative) embodied energy is about 1580 MJ/kg. Needs to be checked in detail. Embodied energy tables for food on Earth do not include solar power but only include energy used for fertiliser production, food production and transformation. This may add about 1o-20 MJ/kg to food.
Wood: At 4 tonnes per hectare for bamboo, embodied energy is about 1200 MJ/kg. Work to transform it into a usable product should be added from table above.
Embodied energy in solar cells
Including cell manufacture, supports and structure. PV cells require very high amounts of energy to manufacture and are likely to be more economical to transport from Earth in the earlier stages of a colony. However, in the long term they produce far more energy than they embody, so solar can be envisioned as a sustainable energy production method for Mars.[2]
| Photovoltaic (PV) Cells Type | Energy MJ per m2 | Carbon kg CO
2 per m2 |
| Monocrystalline (average) | 4750 | 242 |
| Polycrystalline (average) | 4070 | 208 |
| Thin film (average) | 1305 | 67 |
References
- ↑ https://en.wikipedia.org/wiki/Embodied_energy
- ↑ 2.0 2.1 https://greenchemuoft.wordpress.com/2017/12/12/embodied-energy-and-solar-cells/
- ↑ Sunter, D.A., Morrow III, W.R., Cresko, J.W. and Liddell, H.P., 2015, July. The manufacturing energy intensity of carbon fiber reinforced polymer composites and its effect on life cycle energy use for vehicle door lightweighting. In Proceedings of the 20th International Conference on Composite Materials (ICCM), Copenhagen, Denmark.
