Getting March’s surplus to August

SLOP4761 · Week 6 · Preservation, and assembling Assignment 1

Where we are

The last scoping week. Two jobs: size the store, then turn five weeks of unknowns into the measurement register.

Assignment 1 is due at 5 pm on the Friday of week 7.

This week’s question

Your garden produces a glut, then produces very little. The household eats at a constant rate all year.

How much of the peak must you move into the trough, what does that take in space and energy, and when does preserving cost more than it saves?

Note what this week is not. Fermentation creates no calories. It moves them through time, and loses some in transit.

By the end you can

  1. Size storage from a harvest curve against a flat consumption curve
  2. State loss terms as assumptions you can defend by order of magnitude
  3. Assemble a measurement register in which every row settles a decision

Harvest against consumption

From week 2 you have a monthly yield curve. Draw consumption flat across it.

  • Surplus — the area above the line
  • Deficit — the area below it

Storage is sized on the smaller of the two. Preserving more than the trough can absorb is a slower way of composting it.

Three losses to carry, each stated as your own assumption: trimming and preparation, fermentation mass loss, and the fraction that fails or is not eaten.

Safety: one recipe, its own conditions

The National Center for Home Food Preservation sauerkraut method, from USDA Agriculture Information Bulletin 539:

  • 25 lb cabbage to ¾ cup canning salt — about 2.25 % salt by weight
  • Ferment at 21–24 °C, “fully fermented in about 3 to 4 weeks”

This is the only place in the course where a number could hurt somebody, so it is the one place the course refuses to generalise.

Four things that method does not say

  1. It states no pH figure at all. The 4.6 threshold is US food law, for sealed shelf-stable product
  2. The numbers do not transfer to other vegetables
  3. Do not reduce the salt. The source is explicit
  4. It is US extension guidance; there is no Australian equivalent

You design capacity. You make and eat nothing for this course.

Worked example: Adelaide

Annual mean 17.0 °C, no frost days, a long dry autumn. The fermentation space needs no heating and no cooling in any month, so its counted energy load is zero, and the bench sits inside 21–24 °C for most of the useful season.

Adelaide’s harvest curve is also the most concentrated — winter rain against summer demand. More surplus arriving at once, and a longer trough to cross.

Darwin and Alice Springs will not get zero, and the control load they write down here is one of the few things that can push a design past 5 kWh/day.

Then: assemble Assignment 1

Decisions first, measurements second.

  • Write the decisions: connect the house roof or not; keep fish or not; rear indoors or out; plant G3 or leave it lawn
  • Then attach measurement rows: what, which decision, method, location, units, frequency, accuracy, cost
  • Cross-check both ways. Every row points at a decision. Every decision has a row
  • Total against the $1,500 investigation allowance, and record what you dropped

Your tutorial task

Part one, 35 minutes: the store, in kg and litres, with a floor area and any control load.

Part two, 55 minutes: sheet 3, at least twelve complete rows, costed.

Output: a sized preservation store, and a measurement register ready to become Assignment 1.

Before you leave

  • Is the store sized on the smaller of surplus and deficit?
  • Does every register row have all ten columns filled?
  • Does every decision have at least one row behind it?
  • Is the total inside $1,500, with the headroom written down?

Full sources in the week 6 notes and the measurement primer.