Embodied energy

Embodied energy 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)
• Note that for all wood, paper, fiber and other biologically produced products, as well as for many plastics, the energy cost of biomass should be added to the embodied energy.

Material	Energy MJ/kg	Density kg /m3	Mars notes	Source
Water	0,5	1000	Melting or condensing from atmosphere	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
Nitrogen	1	1	Absorption using fibes and pressure differentials	ML
Ammonia NH3	55	0,73	16% of the mass of protein is nitrogen. Hydrogen need to be produced by electrolysis, then combined with compressed atmospheric nitrogen and turned into ammonia via the Haber-Bosch.
Propellant (CH4)	127		This includes the energy to produce the corresponding Oxygen, atmospheric compression and hydrogen electrolysis. The residual energy density of methane is 53,6 MJ/kg.	ML
Food and biomass	1300	900-1000	Based on 250 W/m2 lighting and 60 mT/ha/y food production. This energy produces an equivalent yield of biomass. Food provides, on average, 3.87 MJ of energy per kg.	ML
Aggregate	0.083	2240	This is the energy required to crush and sort the aggregate that is used for concrete production or road building
Compressed Regolith Blocks (CRB)	0,5	2000	5% cement	ML
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
Glass	15	2500	Primary glass production. Toughened glass reaches 23 MJ/kg
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.
Aluminium (general & incl 33% recycled)	155-220	2700	Alumina is common, but perhaps not in concentrated ores
Copper (average incl. 37% recycled)	42-140	8600
Lead (incl 61% recycled)	25.21	11340
Nickel	165	8908
Gold	310000	19300
Platinum	190000	21447
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
Medium-density fibreboard	11	680–760
Plywood	15	540–700
Plasterboard	6.75	800
Gypsum plaster	1.8	1120
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
Ceramic sanitary ware	29
Paint - Water-borne	59
Paint - Solvent-borne	97
Carbon fiber composite	800	1800-2000
Solar cells	2088		Silicon cells, not installed.

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 is included, although these are for feedstocks on Earth. The feedstock energy on Mars is probably higher as it is all sourced from methane.

Aluminium requires much more energy than Steel or iron and therefore is less likely to be used for construction on Mars. However, both steel and aluminium production on Earth uses coke, that embodies significant energy that is not counted in the evaluation made for Earth but would need to be added for Mars . TBC.

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 60 tonnes per hectare, or 6 kg/m2, embodied energy is: 250 W/m2 x 24 x 365 x 3600 / 6kg/m2 = 1300 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 fertilizer production, food production and transformation. This may add about 10-20 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. On Earth solar cells produce their embodied energy in about one year or less. Mars should require 2+ years due to the lower solar constant.

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

Embodied energy in consumer goods

From the University of Calgary Energy education website. For the table below the values are an aggregate of all of the energy within the objects, so there is no mass unit included, rather it is the amount of energy in the entire object.

Embodied energy in objects

	Embodied energy (MJ/functional unit)
Hair dryer	79
Coffee maker	184
LCD monitor	963
Smartphone	1,000
PC tower	2,085
Washing machine	3,900
Laptop	4,500
Refrigerator	5,900
Digital copier	7,924
Cell tower	100,000

Discussion

Since biomass is produced at the same time as food in roughly equivalent quantities, it might be better to divide the energy of food into two, and ascribe half the energy to biomass. The biomass energy can then be added to products derived from biomass.