Compost, fertiliser and getting seeds

A greenhouse that only delivers food is only half the job. The other half is the cycle: seeds for the next sowing, leftovers and spoiled food back into the soil. This article shows what the game data says about it – and where it is silent.

The cycle#

1. Plants grow in the tray and bear fruit, later seeds.
2. Fruit is eaten, cooked or processed. Whatever is left or spoils goes into the composter.
3. The composter delivers fertiliser, which goes into the tray's fertiliser slot.
4. You store seeds for the next round.

What decays and what does not#

Fresh crops do not last forever. According to the game data all crops have a decay rate of 0.00018, cooked dishes a similar one (0.00018 to 0.00026). How many minutes that is exactly the rate alone does not tell you – in the game it also depends on temperature and pressure.

These do not decay:

• seeds of every kind,
• canned food from the packaging machine, such as tomato soup or corn soup,
• fertiliser.

Spoiled food becomes decayed food. You do not have to throw it away: that is exactly what the composter is for.

The two composters#

	Advanced Composter	Portable Composter
Type	fixed	portable
Power	10 W, 100 W more while composting	battery in its own slot
Connections	chute in and out, liquid inlet, power, data	none
Water	20 mol per fertiliser from the pipe	20 mol per fertiliser from the liquid canister
Grinding	1.5 s per item	5 s per item
Composting	60 s per fertiliser	120 s per fertiliser
Logic	yes (On, Activate, Quantity …)	no
Production	kit, electronics printer tier 2	directly in the electronics printer
Cost	15 copper, 30 steel, 20 electrum, 5 solder + 5 steel sheets	15 copper, 10 steel

How the composters work#

The process has two steps. First the composter grinds whatever lies in its import slot into its stock, one item at a time. While it grinds, Mode is 1, otherwise 0. The device sets this itself – so Mode0 and Mode1 are not a switch but a display. On the large composter you read the stock as Quantity.

Then it composts: you press the button or write Activate 1. That only works with at least 3 items in stock and at least 20 mol of water. Every 3 items and 20 mol of water make one fertiliser. The composter keeps going until fewer than 3 items are left or the water runs out, then Activate drops back to 0 by itself.

A worked example: 30 potatoes in the large composter take 30 × 1.5 s = 45 s of grinding, then 10 × 60 s = 10 minutes of composting. The result is 10 fertiliser, and 200 mol of water are used.

What they accept differs:

Stock	large composter	portable composter
normal food	plants only: crops and seed packets	anything edible, cooked food too
decayed food	Decayed Food	Decayed Food
biomass	Biomass and Hay	Biomass and Hay

Seed packets count as plants in the game. So do not sort seeds into the composter line, or they become fertiliser.

While composting, both devices release gas and a little heat into the room, nitrogen and methane according to the Stationpedia. The amounts are only stored in the prefab and were not extracted. Methane is flammable – a composter belongs in a ventilated room.

The large composter fits well at the end of a chute line: a sorter diverts spoiled food from storage, and the composter takes it in through its chute input. How that works is covered in Sorters, stackers and chute valves with logic.

Fertiliser#

Fertiliser goes into the second slot of the Hydroponics Tray, which the game calls "fertiliser". No printer has a recipe for it and no trader sells it. You have to compost fertiliser yourself.

Every fertiliser carries three values. This is how they work according to the game code:

Value	Base	Effect
GrowthSpeed	1	factor on the plant's growth rate and healing
HarvestBoost	1	this many extra fruits per harvest, rounded to a whole number
Cycles	2	one item lasts for this many plantings, then it is used up

Timing matters: fertiliser takes effect when a plant is placed in the tray. Perennials such as tomato and pumpkin take another dose each time they regrow after a harvest. If the fertiliser only goes into the slot while the plant is already growing, that round gets nothing. So: fertilise first, then plant.

How good the fertiliser is depends, in the large composter, on the mix in its stock:

• GrowthSpeed = 1 + 0.25 × share of decayed food, at most 1.25
• HarvestBoost = 1 + 1.5 × share of plants, at most 2.5
• Cycles = 2 + 5 × share of biomass, at most 7

A worked example: decayed food only gives GrowthSpeed 1.25. A potato is then ripe after about 2,400 s instead of 3,001 s. Potatoes only give HarvestBoost 2.5, rounded 2 extra fruits per harvest. Biomass only gives 7 plantings instead of 2.

The portable composter calculates the shares as whole numbers. It only gives a bonus when its stock consists of a single kind. Any mix gives plain fertiliser with the base values.

The Greenhouse planner calculates without fertiliser. Anything fertiliser adds is a bonus.

Getting seeds#

Every plant goes through several growth stages. Once it is ripe you can harvest. If you wait longer, it reaches the last stage: ripe and with seeds. According to the game data this stage does not end by itself, so the plant waits for you.

Plant	ripe after	seeds from	extra wait for seeds
Potato	3,001 s	4,001 s	1,000 s
Wheat	2,701 s	3,601 s	900 s
Rice, soybean, mushroom	3,601 s	4,801 s	1,200 s
Fern	2,401 s	3,201 s	800 s
Corn	7,201 s	9,001 s	1,800 s
Tomato	11,701 s	14,401 s	2,700 s
Pumpkin	14,401 s	16,801 s	2,400 s

A worked example: a potato is ripe after 3,001 s. If you wait another 1,000 s you get seeds. Potatoes can also be planted again directly, though – so you can weigh whether you prefer 1,000 s of waiting or one potato less on your plate. The greenhouse planner works through both routes.

The best place to store seeds is the Appliance Seed Tray on a bench: twelve slots, and seed does not decay.

Buying seeds#

The hydroponics trader (classes basic and medium) stocks seeds, one packet per kind per visit:

Seeds	Price
Potato, tomato, wheat	50
Fern, sugarcane	100
Rice, soybean, switchgrass	200
Cocoa, watermelon, blueberry, strawberry	250
Mushroom, corn	300
Pumpkin	400

Watermelon, blueberry and strawberry are on offer only with a 50 % chance. How to reach a trader is explained in Trading: satellite dish, trader classes, landing pad, all offers are in the trader overview.

Fermentation: alcohol and polluted water#

Fermenting does not happen in the composter but in the Fermenter. It accepts plants, decayed food, biomass and hay through its chute, needs 20 s per item in Active mode and passes the products into its liquid line. According to the game data plants yield liquid alcohol (Liquid Alcohol) and polluted water (Polluted Water), each at 29 °C:

Plant	Alcohol	Polluted water
Corn	40 mol	2 mol
Pumpkin	18 mol	0.9 mol
Tomato	12 mol	0.6 mol
Potato, rice	8 mol	0.4 mol
Wheat, soybean	6 mol	0.3 mol
Mushroom, fern	2 mol	0.1 mol

Liquid alcohol is a fuel. According to the combustion table it burns with oxygen at a ratio of 1 : 3 into carbon dioxide and steam: 1 mol of alcohol and 3 mol of oxygen give 8 mol of CO₂ and 2 mol of steam. The 40 mol from one corn cob would therefore need 120 mol of oxygen. Because the fermenter pushes everything into its line, the alcohol stays in the pipe. It only becomes dangerous if the line leaks or you empty it into a room with breathing air.

Biomass#

Biomass is listed as an ore in the game. In the furnace, advanced furnace and arc furnace it smelts into charcoal; the centrifuge produces it. In the composter, biomass and hay count towards the biomass stock. The higher their share, the more plantings the fertiliser lasts.

Next steps#

• Plant values in detail: Farming: light, water, temperature and air for plants
• Beds, water and automation: Hydroponics and planters: setup and automation
• Sorting out spoiled food automatically: Sorters, stackers and chute valves with logic
• All plants: Plants