Most explanations of life cycle assessment stop at the framework diagram. This life cycle assessment example goes the other way: one process, carried through all four ISO 14040 phases, with every number shown and the arithmetic left visible so you can check it. The case is a 2000 L single-use CHO fed-batch producing a monoclonal antibody, but the method transfers to any manufacturing process.
The interesting part of any life cycle assessment example is not the final number. It is which input turns out to control it, and how badly a plausible-looking choice in Phase 1 can distort everything downstream.
What a life cycle assessment actually is
A life cycle assessment is a structured accounting of the environmental flows crossing the boundary of a defined system, normalised to a defined unit of output. That is the whole idea. Everything else is bookkeeping discipline.
The LCA method is standardised by ISO 14040 (principles and framework) and ISO 14044 (requirements and guidelines). Neither standard tells you which impact assessment method to use or how to allocate between co-products. They define the structure within which you make and disclose those choices. This matters more than it sounds: two competent practitioners can assess the same process and get different answers, both defensible, because the standards constrain the process rather than the result.
That is not a hypothetical concern. Herrmann and Moltesen modelled identical systems in two leading software packages and found the results diverged, driven by differences in background data and how each implemented the impact assessment methods. If the tool changes the answer, the assumptions certainly do.
The four phases of LCA: the ISO 14040 methodology
The LCA methodology set out in ISO 14040 defines four phases. Three are sequential; the fourth runs alongside the others rather than after them. Each of the life cycle assessment phases below is worked in full further down this page.
Phases one to three run in sequence: goal and scope definition sets the functional unit and system boundary; inventory analysis quantifies the mass and energy balance; impact assessment applies characterisation factors. Interpretation connects to all three and feeds the resulting decisions.
Phase 1: goal and scope, with the functional unit trap
Every life cycle assessment example starts here. Goal and scope fixes three things: why you are doing the study, what the functional unit is, and where the system boundary sits. The functional unit is the one that quietly determines your conclusions.
The functional unit is the reference quantity everything is normalised to. For our example it is one kilogram of purified monoclonal antibody. The obvious alternative, one batch, looks harmless and is not: a batch consumes roughly the same electricity, water and consumables whether it yields 3 kg or 9 kg. Normalise per batch and you make titer invisible. Since titer is the single largest lever available to a process development team, that is a serious error rather than a stylistic one.
For the boundary we use cradle-to-gate: raw material extraction through to purified drug substance leaving the facility. Distribution, cold chain, clinical use and disposal of the finished drug product are excluded. That is conventional for drug substance manufacture, and it must be stated, because a cradle-to-gate number and a cradle-to-grave number are not comparable.
Inputs of media and buffers, water, electricity and single-use plastics cross into the boundary, which contains upstream processing, downstream processing, facility services and waste treatment. One kilogram of drug substance leaves as the functional unit. Fill-finish, cold chain, distribution, clinical use and finished-product disposal are excluded.
Phase 2: building the life cycle inventory
The life cycle inventory is a mass and energy balance for everything crossing the boundary. It is the most laborious phase and it is where most of the study's uncertainty lives.
For our 2000 L vessel at 80% working volume, a 3.0 g/L harvest titer, 70% downstream yield and a 90% batch success rate:
Step 1 — product mass per batch
harvest mass = 1600 L × 3.0 g/L ÷ 1000 = 4.80 kg
after DSP = 4.80 kg × 0.70 = 3.36 kg
expectation-weighted for 90% success = 3.02 kg
The success-rate term matters. A failed batch consumes every input and yields nothing, so it raises the footprint of the batches that do succeed. Ignoring it flatters your result by about 10% here.
Next the energy. Agitation is a specific power draw over time; aeration is compression work; cooling, cleanroom HVAC and water generation are read from facility data. The full inventory for one batch:
| Flow | Quantity | Unit | Note |
|---|---|---|---|
| Agitation energy | 27 | kWh | 0.05 kW/m³ × 1.6 m³ × 336 h |
| Aeration energy | 52 | kWh | isothermal compression, 60% efficiency |
| Cooling | 900 | kWh | chiller duty |
| Cleanroom HVAC | 26,880 | kWh | 80 kW allocated to suite × 336 h |
| WFI / PW generation | 900 | kWh | 15 kWh/m³ × 60 m³ |
| Electricity total | 28,759 | kWh | |
| Process + CIP water | 60,000 | L | buffers dominate |
| Media components | 48 | kg | glucose, salts |
| Single-use polymers | 82 | kg | PE, EVA, PP, PC, PVDF |
That HVAC figure is the one people leave out, and leaving it out is why naive bioprocess footprints come in roughly an order of magnitude too low. The bioreactor is not the energy story. The room around it is.
Build this inventory from your own process
The Bioprocess LCA Calculator takes titer, working volume, aeration, HVAC load, water and single-use masses and assembles the inventory for you, then applies the characterisation factors from the next section.
Phase 3: impact assessment
Impact assessment converts inventory flows into environmental impact using characterisation factors. Our guide to emission factors for bioprocessing lists the open sources for every factor used here. For climate change these are the IPCC global warming potentials, which express each greenhouse gas relative to carbon dioxide over a chosen time horizon.
| Gas | Formula | GWP100 (kg CO2e/kg) |
|---|---|---|
| Carbon dioxide | CO2 | 1 |
| Methane | CH4 | 27.9 |
| Nitrous oxide | N2O | 273 |
| Sulfur hexafluoride | SF6 | 25,200 |
Applying the factors to our inventory:
Step 2 — inventory to CO2e
water 60 m³ × (0.149 + 0.708) kg/m³ = 51 kg CO₂e
media 48 kg × 0.72 kg CO₂e/kg avg = 35 kg CO₂e
resin 82 kg polymers, production = 204 kg CO₂e
incineration 82 kg × carbon fraction × 44/12 = 243 kg CO₂e
TOTAL = 12,036 kg CO₂e / batch
÷ 3.02 kg product = 3,980 kg CO₂e / kg
Components are rounded to whole kilograms for display, so the column sums to 12,037 while the total from unrounded values is 12,036.
Polymer incineration is computed from stoichiometry rather than looked up: every carbon atom in the polymer ends up as CO2, so polyethylene at 85.6% carbon yields 0.856 × 44/12 = 3.14 kg CO2 per kg burned.
Phase 4: interpretation and sensitivity
Interpretation is where a life cycle assessment example earns its cost. A single number is not an answer; the contribution analysis is.
Electricity is 95.6% of the total, and within that, cleanroom HVAC is 93.5% of the electricity. The bioreactor's own agitation and aeration together account for under 0.3% of the footprint. Any decarbonisation plan that starts with the bioreactor is optimising the wrong thing.
Because one input dominates so heavily, the result is essentially a function of grid carbon intensity:
| Grid intensity (g CO2e/kWh) | Example region | Footprint (kg CO2e/kg) |
|---|---|---|
| 50 | Hydro/nuclear-heavy | 652 |
| 134 | Upstate New York | 1,450 |
| 400 | Mixed grid (base case) | 3,980 |
| 700 | Coal-heavy | 6,833 |
Why 3,980 and not 4
Published footprints for industrial fermentation products such as lactic or succinic acid sit around 2–15 kg CO2e per kg. This example lands three orders of magnitude higher, and both figures are correct.
The difference is titer and facility class. A bulk organic acid runs at 50–150 g/L in a non-classified plant with no cleanroom HVAC and minimal water treatment. A monoclonal antibody runs at 1–5 g/L inside a GMP suite whose air handling alone is 26,880 kWh per batch. Same method, same arithmetic, radically different denominator and overhead. Never compare a footprint across product classes without checking both.
Why titer dominates a bioprocess LCA
Titer is the second lever, and for a process development team it is usually the more actionable one. The relationship is exactly inverse.
| Titer (g/L) | Product per batch (kg) | Footprint (kg CO2e/kg) |
|---|---|---|
| 1 | 1.01 | 11,940 |
| 2 | 2.02 | 5,970 |
| 3 | 3.02 | 3,980 |
| 5 | 5.04 | 2,388 |
| 10 | 10.08 | 1,194 |
This is why the functional unit choice in Phase 1 was not a technicality. Had we normalised per batch, every row of that table would read 12,036 kg CO2e and the most important finding in the study would have been invisible.
It also reframes what counts as a sustainability project. A titer improvement from 3 to 5 g/L, which a cell line and media programme might deliver, cuts the footprint by 40%. Bunnak and colleagues found the same structural effect when comparing fed-batch against perfusion: the process configuration that produces more product from the same facility footprint wins on both cost and environmental impact, and the two track each other closely.
If the result is headed for a corporate disclosure rather than a process decision, see how this inventory maps onto Scope 1, 2 and 3 reporting.
Five mistakes that invalidate an LCA
Working through a life cycle assessment example end to end exposes the failure modes. These are the ones that turn a defensible study into a misleading one.
- Normalising per batch instead of per unit of product. Hides titer, yield and success rate, which are usually the largest levers.
- Omitting facility services. Cleanroom HVAC and water generation dominate at 93.5% and 3.1% of electricity here. A model containing only the bioreactor lands roughly an order of magnitude low.
- Comparing numbers from different boundaries. A cradle-to-gate figure against a cradle-to-grave figure is not a comparison. Neither is one study's number against another's if the grid factors differ.
- Not stating the grid factor. The same process spans 652 to 6,833 kg CO2e/kg across plausible grids. A footprint quoted without its grid assumption is close to meaningless.
- Treating a screening result as a verified one. Screening finds hotspots. Environmental Product Declarations and audited disclosures need licensed background data and third-party verification.
Compare the cost side of the same process
Carbon and cost of goods are driven by the same inputs. The Fermentation Economics Calculator uses titer, yield and duration to give cost per gram, so you can see both consequences of a process change together.
Frequently asked questions
What are the four phases of a life cycle assessment?
ISO 14040 defines goal and scope definition, life cycle inventory, life cycle impact assessment, and interpretation. The first three are sequential. Interpretation runs alongside them, feeding findings back into scope and inventory as the study develops.
What is a functional unit in LCA?
The reference quantity that all inventory data is normalised to, and the most consequential choice in the study. For a bioprocess it should be one kilogram of purified product rather than one batch or one litre of culture, because a per-batch basis makes titer and yield invisible.
What is the difference between cradle-to-gate and cradle-to-grave?
Cradle-to-gate stops when the product leaves your facility. Cradle-to-grave continues through distribution, use and end of life. Most drug substance studies are cradle-to-gate. The two are not interchangeable and the choice must be declared.
How do you calculate CO2e in a life cycle assessment?
Multiply each inventory flow by its characterisation factor and sum. For climate change the factors are IPCC global warming potentials: on the AR6 100-year basis, methane is 27.9 and nitrous oxide is 273, so a kilogram of methane counts as 27.9 kg CO2e. Divide the total by the functional unit.
Why does titer matter so much in a bioprocess LCA?
Because the burden is fixed per batch while the product mass is not. HVAC, water generation, cooling and consumables barely move when titer doubles, so the footprint per kilogram halves. In this example, 1 g/L gives about 11,900 kg CO2e/kg and 10 g/L about 1,190.
Can I do a life cycle assessment without buying software?
For a screening study, yes. With a mass and energy balance and published open emission factors, a spreadsheet or a purpose-built calculator gives a defensible directional answer. Licensed software and a commercial background database become necessary when the result must be externally verified.
References
- Herrmann, I.T. & Moltesen, A. (2015). Does it matter which Life Cycle Assessment (LCA) tool you choose? A comparative assessment of SimaPro and GaBi. Journal of Cleaner Production. doi:10.1016/j.jclepro.2014.08.004
- Pietrzykowski, M., Flanagan, W., Pizzi, V., Brown, A., Sinclair, A. et al. (2013). An environmental life cycle assessment comparison of single-use and conventional process technology for the production of monoclonal antibodies. Journal of Cleaner Production. doi:10.1016/j.jclepro.2012.09.048
- Bunnak, P., Allmendinger, R., Ramasamy, S.V., Lettieri, P. & Titchener-Hooker, N.J. (2016). Life-cycle and cost of goods assessment of fed-batch and perfusion-based manufacturing processes for mAbs. Biotechnology Progress. doi:10.1002/btpr.2323
- Alves, V.S.S., Bianchini, V.K., Bezerra, B.S., Razzino, C.A. et al. (2025). No One-Size-Fits-All: A Systematic Review of LCA Software and a Selection Framework. Sustainability. doi:10.3390/su18010197