Our review method: how we translate marketing claims into real composting behaviours
Most compost bin reviews rely on star ratings or short-term impressions. We take a different approach. Our reviews focus on how bins actually behave over time, once biological limits, material behaviour, and real-world trade-offs are accounted for.
This page explains our scoring process and how it connects to the detailed claim-by-claim assessment used in our reviews.
Our scoring process
We use a balanced scorecard rather than a single overall verdict. Each compost bin is assessed across multiple dimensions that reflect real composting behaviour, including design-related biological constraints, compost outcomes, nuisance risk, and usability trade-offs. This prevents strong performance in one area from masking clear limits in another.
Scores are expressed on a 0–10 scale for each category and are designed to be comparative rather than absolute. Because scores are derived from multiple weighted aspects, bins often score highly in some areas and lower in others. When normalised, this typically results in a narrower spread of scores, commonly clustering between 5 and 8 out of 10. As a guide, scores of 7–8 indicate stronger overall alignment, 5–6 indicate moderate alignment, and scores below 5 indicate clear limitations. These scores describe relative alignment with realistic composting behaviour under typical domestic conditions, not guaranteed outcomes.
Value-for-money (VfM) is considered separately. It reflects the relative amount of real composting capability a bin delivers for its price, after accounting for size and composting method, rather than assuming that higher cost automatically delivers better composting results.
To keep this easy to interpret, we group bins into value bands rather than relying on raw numbers alone. These bands are: Excellent, Good, OK, Poor.
How we translate claims into scores
Marketing language often blends convenience features with implied biological outcomes. To avoid this, we translate claims into a structured scoring matrix. Each claim area below explains:
- what is typically implied in marketing,
- how that implication is bounded by composting reality,
- and how those boundaries affect scoring.
The sections that follow set out this translation framework in full.
Composting process claims
Typical marketing claim:
The bin “does the composting,” “creates the right conditions automatically,” or “maintains aerobic composting throughout.”
How we score it:
Composting is a biological decomposition process carried out by microorganisms. A compost bin does not compost material by itself; it shapes conditions that may support microbial activity. Oxygen availability within composting material is uneven, and even bins described as “aerated” contain a mix of aerobic, low‑oxygen, and anaerobic micro‑zones. Aerobic dominance is managed, not guaranteed by design alone.
What this means in practice:
Claims are scored on whether they acknowledge that composting outcomes depend on conditions and management, not on the bin acting as an active composting device. Language implying automatic or uniform biological control is downgraded.
Speed and performance claims
Typical marketing claim:
The bin “speeds up composting,” “produces compost faster,” or “delivers quick results.”
How we score it:
Time to usable compost is not a fixed property of a bin. Decomposition speed varies with input materials, moisture balance, oxygen availability, system volume, ambient conditions, and what is meant by “finished compost.” Faster decomposition under some conditions may trade off against heat retention, moisture stability, or biological continuity.
What this means in practice:
We treat speed claims as incomplete unless their limits are made explicit. Performance language is interpreted as conditional rather than absolute, and any suggestion of predictable timelines is discounted.
Resulting compost — material reality
Typical marketing claim:
The bin “produces finished compost,” “creates uniform compost,” or “delivers ready‑to‑use material.”
How we score it:
Compost is not a single uniform material. Domestic compost contains multiple fractions at different stages of decomposition, including partially decomposed organic matter, stabilising material, biologically inactive residues, and living or dormant microorganisms. Compost does not mature uniformly throughout a bin, and material removed from an access point may be mixed‑stage or wetter than surrounding material.
What this means in practice:
We score claims against whether they recognise compost as heterogeneous and staged. Statements implying uniform maturity or guaranteed readiness are treated as over‑simplifications.
Compost, microbes, and soil biology
Typical marketing claim:
The bin “creates beneficial microbes,” “builds healthy soil biology,” or “inoculates soil with life.”
How we score it:
Microorganisms active during composting are primarily decomposers adapted to breaking down organic inputs. They are not equivalent to soil symbionts. Applying compost to soil does not transfer a complete or permanent soil biology. The primary soil benefit of compost is the addition of carbon substrates and nutrients that support soil food‑web processes after application.
What this means in practice:
Claims are accepted only when they describe compost as a source of processed organic material, not as a biological inoculant. Any implication of guaranteed soil biological outcomes is scored as non‑compliant.
Microbes, composting, and soil biology — canonical claims block
Composting is a process state, not a microbial product. Microbial communities within a compost bin are transient and shift with feedstock, conditions, and time. There is no single compost microbiome, and composting does not reliably curate a predictable or transferable soil biology.
Finished compost is a heterogeneous organic input, not soil and not, in most domestic systems, stable humified organic matter. When compost is applied to soil, the most reliable effect is the addition of biologically processed organic substrates that can fuel existing soil food webs. Living microbes, dormant forms, and microbial residues may be present, but their persistence and function are determined by soil conditions, not by the composting process. In principle, under tightly controlled conditions, further stabilisation of organic matter may occur before soil application, but this is not assumed and must be treated as conditional rather than typical.
Odour, temperature, and ‘sanitisation’ claim patterns
Typical marketing claim:
The bin is described as “odour‑free,” “smell‑free,” “hot composting,” or as able to “kill pathogens and weed seeds” through high temperatures.
How we score it:
Odour, temperature, and sanitisation outcomes are emergent properties of the composting process, not fixed features of a bin. Odour formation reflects the interaction of moisture balance, oxygen availability, material composition, and micro‑zone behaviour. Temperature rise depends on the balance between microbial heat generation and heat loss, which is influenced by multiple system and environmental factors. Claims implying guaranteed sanitisation or biological neutralisation exceed what bin design alone can ensure.
What this means in practice:
We treat odour‑free, hot composting, and sanitisation claims as conditional and context‑dependent. Absolute language suggesting consistent smell elimination, reliable high‑temperature operation, or assured biological neutralisation is downgraded unless explicitly bounded.
Input materials — scope and constraints
Typical marketing claim:
The bin “accepts all kitchen waste,” “handles everything,” or “composts all inputs equally.”
How we score it:
All plant and animal matter is ultimately biodegradable, but domestic composting performance depends on time horizon, moisture balance, oxygen availability, and system behaviour. Claims about acceptance describe theoretical biodegradability, not guaranteed performance. High-moisture, high-fat, or high-protein inputs increase the likelihood of odour, pest attraction, and prolonged decomposition.
What this means in practice:
We distinguish between what can be added in principle and what performs predictably. Phrases such as “can accept” are not scored as promises of speed, cleanliness, or low risk.
Capacity, throughput, and time-horizon claims
Typical marketing claim:
The bin is described as “large enough for a household,” “high capacity,” or “able to keep up with regular food waste.”
How we score it:
Capacity claims often conflate container volume with processing throughput. Compost bins process material over time, and unused volume does not equate to available processing capacity. Throughput depends on the rate of input, the rate of decomposition, and the residence time required for material to stabilise. Claims of suitability are incomplete without acknowledging these constraints.
What this means in practice:
We score capacity language as conditional. Statements that imply continuous or guaranteed handling of inputs without reference to time horizon or processing limits are downgraded.
Pests — risk framing
Typical marketing claim:
The bin is “pest‑proof,” “rodent‑proof,” or “prevents pests.”
How we score it:
Compost bins reduce pest access but do not eliminate pest risk. Pest presence depends on exposed attractants, moisture imbalance, access opportunities, and local pest pressure. Claims of resistance refer to physical deterrence, not biological immunity.
What this means in practice:
We score pest claims as risk‑reduction statements, not guarantees. Absolute language is treated as marketing shorthand rather than literal protection.
Usability and handling claims
Typical marketing claim:
The bin is described as “easy to use,” “low effort,” “no turning required,” or “maintenance‑free.”
How we score it:
Usability features relate to handling and convenience, not to composting biology. Ease of loading, unloading, or reduced intervention does not determine microbial pathways, composting speed, or material uniformity. Claims that present reduced effort as a guarantee of composting outcomes conflate usability with biological performance.
What this means in practice:
We score usability claims as trade‑offs. Convenience features may reduce effort but can also introduce constraints or risks elsewhere. Statements implying that ease of use removes biological limits are downgraded.
Leachate and liquid by‑product claims
Typical marketing claim:
The bin “produces liquid feed,” “has no leachate,” or “collects useful compost tea.”
How we score it:
Liquid by‑products are not a fixed or guaranteed feature of composting systems. Their presence often reflects moisture balance, compaction, and material breakdown rather than optimal composting conditions. Claims that frame liquids as inherently beneficial or absent by design exceed what bin structure alone can ensure.
What this means in practice:
We treat liquid and leachate claims as conditional. Assertions that liquid outputs are consistently beneficial, harmless, or eliminated by design are downgraded unless clearly bounded.
Canonical summary principle
Typical marketing claim:
Convenience features are presented as direct biological outcomes.
How we score it:
Most compost‑bin claims conflate usability with composting results. Canonically, bins are condition‑shaping, risk‑reducing systems. They influence probabilities and trade‑offs; they do not guarantee outcomes.
What this means in practice:
Our reviews reward clear boundaries and downgrade claims that imply certainty where only conditional behaviour exists. Every score reflects limits as well as benefits. well as benefits. only conditional behaviour exists. Every score reflects limits as well as benefits.