How much carbon do we save when flowers and produce move from air to sea? The numbers, explained

How much carbon do we save when flowers and produce move from air to sea? The numbers, explained

Hook: You care about cleaner food and honest sustainability claims—but does that pretty bouquet or imported mango actually carry a huge hidden carbon bill because it flew instead of sailed? If you buy or source perishables, understanding the emissions difference between air and sea transport isn't academic: it changes supplier choices, pricing, packaging and whether a product can realistically be low-carbon.

Quick answer (in plain terms)

For most long-distance routes, air freight emits orders of magnitude more CO2 per tonne transported than ocean shipping. On realistic routes for perishables, shifting from air to sea typically reduces transport emissions by a factor of 10–50x. That translates to savings measured in kilograms of CO2 per bouquet or per box of fruit—and, at scale, thousands of tonnes of avoided CO2.

Why this matters now (2026 context)

Late 2025 and early 2026 saw growing momentum—especially from exporters in East Africa and importers in Europe—to trial and scale modal shift programs for flowers, fruit and vegetables. Policymakers and retailers are tightening supply-chain carbon transparency (Smart Freight Council/GLEC uptake, expanded EU reporting), and logistics players are improving reefer reliability and controlled-atmosphere sea containers. That means modal shift is no longer just a theoretical climate win; it is a commercial and regulatory opportunity.

How we quantify emissions: the metrics and assumptions

Transport emissions are typically reported as grams of CO2 per tonne-kilometre (gCO2/tkm). That lets us compare modes regardless of load size or distance.

• Air freight (wide range): Common published ranges put air freight at roughly 500–1,500 gCO2/tkm for cargo carried in modern passenger flights or dedicated freighters; heavy long-haul charters can be higher. (Sources: IATA/industry lifecycle analyses, ICCT summaries 2020–2025).
• Ocean container shipping: Typical container shipping averages are in the order of 5–20 gCO2/tkm; modern slow-steaming container vessels push the lower end. Reefer containers (refrigerated) add electrical energy use, raising the effective number—so for refrigerated perishables a realistic range is 8–30 gCO2/tkm, depending on vessel efficiency and route.

Important: these are ranges. We'll show transparent calculations with distance and per-unit examples so you can adapt to your route and product.

Concrete example: roses from Nairobi to Rotterdam

Let's run a simple scenario so the numbers feel tangible. Distances and assumptions are conservative and rounded for clarity; change them to match your route.

Assumptions

• Route (air): Nairobi → Amsterdam/Rotterdam ≈ 6,700 km (direct flight distance).
• Route (sea): Mombasa → Rotterdam via Suez ≈ 10,000 km (port-to-port sea distance + hinterland movements).
• Cargo mass: 1 tonne (1,000 kg) of cut flowers (roughly 1,500–2,000 bouquets depending on bouquet size).
• gCO2/tkm ranges used: Air = 500–1,500 g, Sea (reefer) = 10–25 g.

Calculations

Air freight emissions per tonne:

Low air: 6,700 km × 0.5 kg/tkm = 3,350 kg CO2 (3.35 tCO2) per tonne
High air: 6,700 km × 1.5 kg/tkm = 10,050 kg CO2 (10.05 tCO2) per tonne

Sea freight emissions per tonne (reefer):

Low sea: 10,000 km × 0.01 kg/tkm = 100 kg CO2 (0.10 tCO2) per tonne
High sea (reefers & older vessels): 10,000 km × 0.025 kg/tkm = 250 kg CO2 (0.25 tCO2) per tonne

Savings from modal shift (per tonne):

Low-case savings: 3,350 − 250 = 3,100 kg CO2 avoided per tonne
High-case savings: 10,050 − 100 = 9,950 kg CO2 avoided per tonne

Per-bouquet view (assume 2,000 bouquets per tonne ≈ 0.5 kg each):

Air (low): 3,350 / 2,000 = 1.68 kg CO2 per bouquet
Sea (high): 250 / 2,000 = 0.125 kg CO2 per bouquet
Approx. savings per bouquet: 1.55–4.95 kg CO2

Bottom line: shifting a single tonne of cut flowers from air to sea can avoid between ~3 and ~10 tonnes of CO2 on a typical long route. That’s a substantial per-tonne and per-bouquet difference.

Apply the same logic to fruit and vegetables

Heavier products like avocados or mangoes are even more impactful per unit if they can move by sea. Because they’re heavier per sale unit, the absolute tonne-based savings multiply. But perishability, ripening and shelf life matter: some fruit must ripen in transit or be harvested earlier if sea shipping is used.

Example: 1 tonne of avocados (hypothetical)

• Assumed route: Central America → Europe – air 6,000 km; sea 10,500 km.
• Using the same gCO2/tkm ranges, potential savings are in the 2–8 tCO2 per tonne range depending on assumptions.

Key insight: for many high-volume perishables, modal shift delivers large absolute emissions reductions when feasible.

Tradeoffs and practical constraints

Modal shift is powerful, but it is not a free lunch. Smart implementation requires managing tradeoffs.

1. Longer transit times

• Air: Hours-to-days. Sea: Days-to-weeks. Longer times increase product risk and inventory lead time.
• Solution: invest in pre-cooling, digital temperature monitoring, controlled-atmosphere (CA) sea containers, better cultivar selection and ripening protocols. Many East African exporters piloted CA reefers in late 2025 to protect roses and citrus on 10+ day voyages.

2. Cold chain and energy use for reefers

• Reefer containers consume electricity; some ports rely on fossil-based power. That raises per-tonne sea emissions—but even with a reefer penalty the sea option usually remains far lower in CO2 than air.
• Solution: use energy-efficient reefers, portable power and shore-power where available, and verify the grid carbon intensity at ports/regions in your footprint.

3. Packaging and protective measures

• Sea-travel requires sturdier packing and sometimes modified-atmosphere packaging. That can add material impact—cardboard, liners, ethylene scrubbers—reducing but rarely erasing modal-shift climate gains. Read vendor field reporting on composable packaging & freshness for practical lessons on materials and handling.
• Solution: use recyclable/compostable packing, lighter weight designs, and reuse schemes for protective crates; optimize palletization to reduce empty space.

4. Market expectations (freshness & speed)

• Some customers expect ultra-fresh items within days. For premium fresh-cut flowers or ready-to-eat fruit, air remains the tool for guaranteed short lead times.
• Solution: hybrid approaches—sea for baseline volumes and air for top-up express shipments—or local-season alignment (import less when local supply is available). Retailers experimenting with local activations and sales windows can combine modal shift with micro-events and micro-markets to meet customer freshness expectations.

5. Spoilage risk and product loss

• Longer transit can raise spoilage if the cold chain fails. Losses erode climate benefits and margins.
• Solution: invest in monitoring (IoT temperature sensors), contractual SLAs with carriers, and contingency ripening/inspection hubs in destination ports.

Real-world modal shift approaches that work

Across the industry, three practical strategies have surfaced as high-impact and relatively low-risk:

1. Controlled-atmosphere (CA) sea freight

CA containers slow ripening and prolong shelf life—turning a 20-day sea voyage into a viable option for many fruits and some flowers. Since late 2024 and into 2025–26, consignments using CA reefers show markedly reduced spoilage rates in pilot programs. For practical packing and CA lessons, see experience from exporters and shipping-focused writeups like sourcing and shipping guides that cover handling fragile, high-value loads.

2. Sea + short-air hybrid (sea for bulk, air for top-up)

Retailers often accept a mixed approach: main volumes travel by sea, while small express air shipments cover uneven demand or highly time-sensitive orders. This keeps overall emissions low while preserving service levels.

3. Origin consolidation hubs

Collect, pre-cool and consolidate across farms into optimized reefers. Pooling product reduces partial loads and the likelihood of empty space—which increases per-unit emissions. Directory and marketplace trends around local listings and consolidation are covered in broader industry overviews like directory momentum and micro-pop-up strategies.

How to calculate your own modal-shift impact (step-by-step)

Use this simple method to estimate savings for a specific product and route. Be transparent about assumptions.

1. Get distance (km) for both air and sea port-to-port routes.
2. Choose gCO2/tkm values for your scenario (air: 500–1,500; sea reefer: 8–30).
3. Multiply distance × gCO2/tkm to get gCO2/t per mode, convert to kg and tonnes.
4. Divide by units per tonne to get a per-product figure (e.g., per bouquet or per carton).
5. Adjust for packaging and cold-chain energy add-ons (add a % penalty for extra packaging and reefer power in your sea estimate).

Example formula (editable):

CO2_per_tonne = distance_km × (gCO2_per_tkm / 1000)
CO2_per_unit = CO2_per_tonne / units_per_tonne

Policy, market and technology trends to watch in 2026

• Stronger logistics emissions reporting: Corporate reporting frameworks and freight MRV (monitoring, reporting & verification) are expanding in 2025–26, so shippers must document modal emissions to meet buyer and regulator demands.
• Green fuel push for shipping: IMO and industry decarbonization targets are accelerating low-carbon fuels for shipping. But full fleet turnover is gradual—modal shift keeps delivering near-term cuts.
• Retailer commitments: Several EU and UK retailers (late 2025 pilots) now include modal-shift clauses in sourcing contracts—the commercial pressure to choose sea for non-time-critical exports is growing.
• Cold-chain tech: Adoption of digital monitoring, composable packaging, shore-power at ports, and efficient CA reefers grew in 2025; expect further cost declines and improved reliability through 2026.

Actionable steps for each stakeholder

For exporters (farm groups, packhouses)

• Run route-level carbon calculations using the steps above and present numbers to buyers.
• Pilot CA reefers and consolidate shipments to minimize empty space and packaging waste.
• Invest in pre-cooling and digital temperature monitoring to reduce spoilage risk.

For importers and retailers

• Set a modal-shift target for non–time-sensitive perishables and include it in supplier KPIs.
• Offer commercial incentives for sea-shipped lines: longer order windows, forecast sharing, and guaranteed volumes to farmers.
• Require transparent freight emission reporting (GLEC framework or equivalent) and reward low-carbon routing.

For consumers and B2C buyers

• Ask retailers for carbon labels or origin-and-mode information. Choose sea-shipped or seasonal local options where freshness allows.
• Support brands that disclose modal emissions and invest in cold-chain transparency.

Common objections—and the answers

“Air keeps product fresher—sea will mean waste.”

True if sea is used without adequate cold-chain or CA. But with modern CA reefers, pre-cooling and ripening hubs, many perishables travel by sea with comparable shelf life. Pilot data from 2025–26 shows spoilage approaching air-shipment levels for several flower and fruit categories when protocols are followed.

“Packaging for sea cancels emission savings.”

Packaging adds impact—but typical packaging increases rarely exceed 5–20% of the transport savings. Using optimized, recyclable packaging keeps the net benefit large. For practical vendor experiences on packaging choices, see composable packaging field reports at flavours.life.

“Switching will cost more.”

Sea is usually cheaper per kilogram. The main costs are capital and process changes (CA equipment, longer inventory). When buyers share risk and forecast certainty, both exporters and importers often see net savings.

Looking ahead: predictions for the next 3 years (2026–2029)

• More retailers will adopt explicit “sea-first” procurement policies for defined perishables categories.
• Reefer efficiency and CA tech adoption will lower the sea-penalty further, increasing feasible product categories for modal shift.
• Freight CO2 reporting will be standardized across more markets—making modal decisions an explicit part of supplier scorecards.
• Hybrid solutions and improved forecasting will reduce the need for air “top-ups,” magnifying cumulative emissions reductions.

Conclusion: the numbers add up—and so does the responsibility

In 2026, moving perishables from air to sea is one of the clearest, verifiable ways to reduce supply-chain CO2 footprints quickly. The per-tonne savings are large; even when you add packaging, cold-chain energy and longer lead times, modal shift typically delivers substantial net reductions. The real work for exporters, retailers and logistics partners is to manage the tradeoffs: invest in cold-chain reliability, refine packaging, share demand forecasts and create blended solutions that preserve freshness while slashing emissions.

Practical next steps (do these this month)

• Run a route-level CO2 comparison for one high-volume product using the calculator steps above.
• Talk to your freight forwarder about CA reefer options and pilot rates for one lane.
• Agree a 90–180 day pilot with a buyer/retailer using sea for base volumes and air for top-ups—monitor spoilage and CO2 outcomes.
• Start reporting freight emissions using a common framework (GLEC/Smart Freight) and share results publicly.

Call to action

If you source or sell perishables, don’t let transport emissions be an invisible externality. Start a modal-shift pilot, demand transparent freight emissions, and work with partners who will invest in CA reefers and cold-chain monitoring. Contact our sustainability team at Kure Organics to get a free route-level emissions template for your key products and a short playbook for a cost-neutral sea-shift pilot. Small changes in routing now can avoid large tonnes of CO2 every year.

“Modal shift isn’t about choosing sea over air for every shipment—it’s about choosing the smarter route for the climate, cost and the consumer.”

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