New studies show scouring and bleaching can slash steam by 60–70% with wastewater heat recovery and low‑temperature agents — and in one modeled setup, total cost fell 63.2%.
In cotton finishing, scouring (an alkaline boiling step that strips waxes and pectins) and peroxide bleaching have long meant near‑boiling baths — and near‑boiling fuel bills. Conventional H₂O₂ bleaching runs at ∼98 °C for 30–60 minutes (pmc.ncbi.nlm.nih.gov). One lab scouring case used 1.5% NaOH at 100 °C for 45 minutes (pmc.ncbi.nlm.nih.gov).
Industry wastes much of that heat. About a third of all energy goes to industry and roughly half is lost as heat (www.mdpi.com). In practice, a typical continuous scouring/bleaching vat discharges wastewater at ~40–60 °C, while the fresh water makeup is near ambient; without recovery, the energy in that hot effluent is lost.
Energy intensity of hot‑liquor finishing
Textile finishing’s large hot‑liquor volumes make it a standout energy sink. The combination of long dwell times (tens of minutes) and near‑boiling temperatures (95–100 °C) drives steam demand in scouring/bleaching, especially with hydrogen peroxide (H₂O₂) systems at ∼98 °C for 30–60 minutes (pmc.ncbi.nlm.nih.gov).
Waste‑heat recovery systems
Routing hot wastewater through heat exchangers to preheat incoming water is now yielding outsized returns. An integrated heat‑recovery design using a heat exchanger plus thermal storage tank cut process heating cost by ~63% in one analysis (www.researchgate.net). In Benninger’s “zero‑discharge” concepts, ultrafiltration/RO reuse of bleaching liquor reached 80–90% and captured up to 70% of its heat (www.fibre2fashion.com). In mills, that translates into preheating fresh water and sharply cutting steam.
These reuse loops commonly deploy ultrafiltration modules; in this context, systems akin to ultrafiltration act as pretreatment before high‑pressure recovery, enabling liquor recirculation alongside the cited 80–90% reuse and up to 70% heat capture (www.fibre2fashion.com).
Effluent‑to‑water preheat and exhaust exchange
Preheating makeup water using hot scouring/bleach effluent via plate or shell‑and‑tube exchangers can recover nearly three‑quarters of the effluent’s energy. One example: lifting fresh water from ~25 °C to ~60 °C recovered ~70% of the effluent heat (www.fibre2fashion.com).
Hot exhaust streams are also recoverable. Heat‑pipe exchangers on fabric heat‑setting machines have been reported to recapture >90% of lost heat to supply process air or boiler combustion air (www.vrcoolertech.com; www.vrcoolertech.com).
Heat pumps and storage integration
Where waste heat is low‑grade (warm rinse water ~30–50 °C), industrial heat pumps can upgrade it. A pilot absorption heat pump running on engine exhaust yielded 34.4 kW cooling from 16 kW waste heat (0.96 COP, coefficient of performance) (www.mdpi.com). Coupling exchangers with heated‑water storage balances batch flows; in one modeled dyeing case, a storage‑integrated system achieved a 63% energy cut with zero drainage losses (www.researchgate.net).
At mill scale, the savings add up. Installing exhaust‑duct boilers and economizers on onsite power generators eliminated ~131,772 MWh/year of fuel use and ~52,700 tCO₂ (www.mdpi.com), with about 80% of the engines’ fuel energy recoverable via waste‑heat recovery systems (www.mdpi.com). One estimate scales potential textile waste‑heat recovery to ~1.02×10^14 kWh/year, saving ~$1.35 billion and ~24.8 MtCO₂ (www.researchgate.net).
Realistic steam reductions in scouring/bleaching
Across studies, heat recovery saves “tens of percent.” For bleaching and scouring, ~60–70% reduced steam usage is realistic (www.fibre2fashion.com; www.researchgate.net), especially when preheating lifts incoming water from ~25 °C to ~60 °C by exchanging with hot effluent (www.fibre2fashion.com).
Where water reuse accompanies heat capture, membrane trains similar to membrane systems can be paired with exchangers to recycle liquor volume alongside thermal energy, aligning with the Benninger approach (80–90% water recycling; up to 70% heat recovery) (www.fibre2fashion.com).
Low‑temperature scouring and bleaching agents
Changing the chemistry cuts temperatures. Enzymatic scouring (using pectinases or lipases) operates at ~50–60 °C and neutral‑to‑mild pH instead of a 100 °C caustic boil. One study applied a pectate‑lyase enzyme at 55 °C for 60 minutes (pH 5–5.5; 0.5–0.8% o.w.f., on weight of fabric) and achieved essentially complete hydrophilicity (wetting time ~4.9 s) with only 3–4% mass loss; enzymatic scouring “uses reduced amounts of water, chemicals, and power” under milder conditions than NaOH (pmc.ncbi.nlm.nih.gov; pmc.ncbi.nlm.nih.gov).
On bleaching, peroxide activators and alternative oxidants lower the heat required. Adding 0.9 g/L glycerol triacetate plus 1.0 g/L peracetic acid (PAA) to H₂O₂ achieved a whiteness index (Berger W) of 61.1 at just 80 °C for 30 minutes — about 97% of the conventional 98 °C result (pmc.ncbi.nlm.nih.gov). PAA at 65 °C on cotton or bamboo gave “strong whitening” comparable to 90 °C H₂O₂ with much less fiber damage (www.researchgate.net). UVA/UV‑assisted systems even run at room temperature: one study reported ~70% less energy than steam bleaching at 98 °C (pmc.ncbi.nlm.nih.gov). Other low‑temperature methods (ozone, ultrasound, microwaves) are also under exploration.
Some mills combine steps in one bath (enzyme plus peroxide, often with mild alkali), reporting 50–70% energy savings due to fewer baths and a lower peak temperature (pmc.ncbi.nlm.nih.gov). Precision feed hardware such as a dosing pump helps control peroxide activators (e.g., triacetin, TAED) or PAA additions at reduced temperatures, supporting the documented outcomes (e.g., 80 °C whiteness index 61.1; ~97% of 98 °C) (pmc.ncbi.nlm.nih.gov).
Performance trade‑offs and savings range
Each low‑temperature method can yield slightly lower absolute whiteness; they’re typically aimed at light colors or targets close to conventional performance (e.g., ~97% white). Still, the energy gains are material: one UVA route cut energy by ~70% (pmc.ncbi.nlm.nih.gov), and an optimized low‑temperature bleach achieved near‑conventional whiteness with reduced energy (pmc.ncbi.nlm.nih.gov). Overall, these chemistries can save 30–60% of the thermal energy in scouring/bleaching, depending on how aggressively temperatures are reduced.
Compounding gains and mill‑level impact
Cutting bleach temperature to 80 °C instead of 98 °C, then sending that 80 °C effluent through a preheater, multiplies the effect — lowering boiler duty even further. Plants adopting charge‑economizers, effluent‑exchangers, or heat pumps on top of advanced chemistry report overall finishing energy falling 20–50%. In a healthcare textile plant, multiple water/energy solutions delivered a 30% reduction in kWh/kg over a year (noted as “around 0,1 – 0,3 kWh/kg”) (detergo.eu). In an example pattern (50 tons/day), Ecolab’s heat‑recovery systems cut both energy and CO₂ by ~30% (detergo.eu).
Technical audits consistently find that 70–80% of heat and water in wet finishing can be reused or saved with today’s technology. Specific markers — “up to 70% heat recovery from bleaching effluent” (www.fibre2fashion.com) and “63% lower fuel costs with one exchanger+storage” (www.researchgate.net) — show the scale. With higher fuel prices and carbon constraints, the economics favor adoption. For Indonesia’s textile sector (or any market), every percentage point of steam saved directly cuts cost and emissions.
Sources and cited studies
Authoritative industry studies and research articles support all figures and claims above. See references in‑line, including ACs Omega (2025) (pmc.ncbi.nlm.nih.gov); Heliyon (2023) (pmc.ncbi.nlm.nih.gov); textile industry reports (www.fibre2fashion.com); case studies and proceedings (www.mdpi.com; www.mdpi.com; www.researchgate.net); UVA/UV‑assisted bleaching research (pmc.ncbi.nlm.nih.gov); and waste‑heat recovery assessments (www.mdpi.com).
