Substrate recipe standardization

Define

Problem Statement

Substrate mixing was performed “by volume and by eye” with each batch varying in composition. This led to:

• Unpredictable batch sizes requiring constant rework
• Unable to forecast pasteurisation capacity requirements
• Regular over-production of mixed substrate exceeding pasteuriser capacity (max 18 bags)
• Waste when batches couldn’t fit into the pasteurisation schedule
• Inconsistent colonisation rates across batches
• Standard bagging practice was ‘fill half the bag’

Project Goal: Standardize substrate recipe and process to eliminate batch variability and reduce waste from 40% to <1%.

Scope

• In scope: Recipe formulation, mixing process, portion control
• Out of scope: Pasteurisation, spawn preparation, fruiting

Team

Role	Name
Process Owner	Adrian Doonan
Subject Expert	Farm operator

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Measure

Baseline Data

Metric	Baseline Value
Mixing batches per week	1-3
Bags produced per batch	4-7 (random)
Percentage waste	~40%
Consistency of bag weight	unknown variation
Time to mix per batch	2.5-3.5 hours

Process Map

Original process: Mix by feel → Check capacity → Decide how many bags to fill → Discard overflow or create backup stock

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Analyse

Root Cause Analysis

Original recipe (by volume, informal):

• Equal scoops of: coffee husks, grounds, hydrated wood pellets
• “A few cups” of gypsum
• Water “to field capacity” with manual squeeze test

Issues identified:

1. Scoops varied in amount (different sizes used informally)
2. “A few cups” was subjective
3. “Field capacity” was under or overshot, needing correction
4. No way to predict finished batch size
5. Pasteuriser capacity (18 bags) was a hard constraint creating downstream decisions in real-time

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Improve

Solution Design

Standardized recipe (the “baker’s dozen” method):

The target was 13 bags per batch to allow 1 buffer:

• 6.0 kg coffee (measured)
• 3.4 kg wood pellets (measured)
• 5.95 l water to hydrate pellets (calculated at standard 1:1.7 ratio)
• 10 scoops coffee husks (this remained scoops as too hard to measure)
• Gypsum: 750g (weighed)
• Extra Water: calculated to reach ~65% moisture content (extra water added as necessary as the moisture content of the coffee grounds varied)

This produces 6.5 × 3kg bags consistently and maximises mixer load. Two mixer runs produce 13 x 3kg bags. Waste is less than a few hundred grams.

Standardized process:

1. Weigh all dry ingredients before mixing
2. Hydrate wood pellets in advance (known absorption rate) across two trays
3. Mix half the ingredients in mixer to avoid bottom layer not mixing correctly
4. Run full ingredients through concrete mixer for fixed duration (12 minutes)
5. Test for field capacity and amend if necessary
6. Portion into pre-staged, unmarked 3kg bags
7. Label bags with batch number, date, coffee source
8. Beginning of mix to ready-for-pasteuriser for 13 bags: 90 minutes

Implementation Timeline

• Week 1: Test recipe, verify bag weight consistency
• Week 2: Run two consecutive batches with new process
• Week 3: Commit to standardized recipe; track waste reduction

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Control

Key Metrics

Metric	Target	Actual (after 4 weeks)
Batch size consistency	±100g	±75g
Bags per batch	13 (fixed)	13
Waste percentage	<10%	0%
Process time (mix only)	90 minutes	85 minutes
Colonisation rate	>95%	97%

Standard Work Documentation

• Recipe details added to shared work tracking app
• Ingredient staging guide (quantities, sources)
• Step by step guide written down and generally understood
• Batch tracking log linked to app

Monitoring & Escalation

• Daily: Visual inspection of mixed substrate consistency
• Per batch: Weight check on 2 random bags
• Weekly: Review colonisation rates by batch and coffee source
• Monthly: Waste trending analysis

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Results

4-week implementation period:

Metric	Before	After	Change
Waste percentage	~40%	0%	-100%
Batch size consistency	Unknown	±75g	Established
Bags per batch	6-18	13	Standardized
Process time (mix only)	2.5-3.5 hrs	85 min	-49%
Colonisation rate	Variable	97%	Stabilized

Economic Impact

• Waste reduction: Eliminated ~€50–100/week in discarded substrate materials
• Capacity utilization: Predictable batch sizes enabled full pasteurizer loading
• Time savings: 45–75 minutes per batch freed for other farm tasks

Lessons Learned

1. Measurement enables standardization. Without weighing ingredients, “by eye” processes can’t be replicated consistently.

2. Buffer capacity prevents waste. The “baker’s dozen” (13 bags) allows for mixing one extra bach if wanting to maximise production to the 18-bag pasteurizer limit while allowing one buffer bag if mixing two mixer loads.

3. Process documentation in app form. Recipe and tracking integrated into the work app ensured the new process was adopted immediately.

4. Coffee source variation requires moisture adjustment. Grounds moisture content varied by supplier, requiring calculated water additions to maintain 65% target.