Palm mills churn out empty fruit bunches (EFB) equal to roughly a quarter of every harvest—leaving operators to choose between soil health and boiler fuel. The catch: EFB’s sky‑high moisture makes it stubborn to burn.
Industry: Palm_Oil | Process: Empty_Fruit_Bunch_(EFB)_Processing
Palm oil mills generate mountains of empty fruit bunch (EFB) waste—fibrous husks left after fresh fruit bunches (FFB) are stripped for oil. Estimates peg EFB at roughly 20–28% of FFB weight (biochartoday.com) (www.envirobiotechjournals.com), with one study noting that 100 tonnes of FFB produce ≈20–23 t of EFB (www.envirobiotechjournals.com).
Scale is enormous: in Indonesia, potential palm oil solid waste (including EFB, shells, fiber) was about 90.3 million tonnes in 2017—enough to supply ~10% of national energy demand (www.envirobiotechjournals.com). A single mill processing ~250,000 t FFB/yr would yield ~48–50 kt EFB/yr (www.researchgate.net). In practice, EFB is often left at or near fields or mills as bulky organic residue.
Mulching and nutrient recycling metrics
EFB is rich in carbon and potassium but low in nitrogen. Analyses of dry EFB fiber show roughly 0.8% N, 0.22% P₂O₅, 2.9% K₂O by weight, plus Mg, Ca and micronutrients, with carbon around ≈42.8% (www.researchgate.net). As mulch or compost, that K‑ and C‑rich organic matter can substitute for chemical fertilizer, especially potash (K‑fertilizer), while sustaining soil organic matter (www.researchgate.net).
Decade‑scale field effects on yield
Trials consistently show soil benefits and yield impacts. A 10‑year Malaysian study (Abu Bakar et al., 2011) found that applying ~30 t/ha/yr of EFB (≈300 kg/palm/yr) significantly increased oil palm yields over 15 t/ha or chemical fertilizer alone; after 10 years, the 30 t/ha treatment boosted soil organic carbon (from ~1.49% to 2.73%) and exchangeable K, and far outperformed 15 t/ha or no‑EFB (chemical‑only) plots in fresh‑fruit yield (www.researchgate.net).
Another Malaysian trial reported that adding 60 or 80 t/ha/yr of EFB (applied annually along alternate frond piles) increased yields and soil fertility vs. no‑EFB controls (www.researchgate.net). In Indonesia, a 15‑year Sumatra study comparing 0, 30, 60, 90 t/ha/yr found only modest yield differences: cumulative yields were ~2.4–5.9% higher under EFB treatments than fertilizer‑only, with no significant loss of yield stability (link.springer.com). EFB mulching sustains or slightly enhances FFB yield while improving soil organic carbon (e.g., +32% SOC under medium‑rate EFB vs control, link.springer.com).
Meta‑analyses across crops echo the trend: one found ~49% higher yields under EFB‑derived mulches or composts vs. no amendment (www.researchgate.net).
Fertilizer substitution and certification pathways
Recycling nutrients via EFB can dramatically cut synthetic fertilizer needs. A recent life‑cycle assessment estimated that EFB‑derived compost as a fertilizer could slash per‑hectare synthetic NPK use by ≈75%, while biochar from EFB still cut NPK by ~35% (biochartoday.com). In long‑running trials, 15–30 t/ha EFB per year raised soil pH (from ~4.5 to 5.5–6.5) and cation exchange capacity (CEC, a soil nutrient‑holding measure) to ~11–13 cmol/kg vs 8.2 in chemical‑only soil over 10 years (www.researchgate.net).
Adoption is widespread because EFB incurs no purchase cost, though its bulk and high moisture make collection and spreading labor‑intensive. Some Indonesian mills are exploring composting solutions—often combining EFB with palm oil mill effluent (POME)—to turn it into certified organic fertilizer; an approved product can earn sustainability credits (www3.wipo.int). A WIPO case study noted mills partnering with bio‑composting firms, creating EFB/POME composts that cut GHG emissions and, once quality‑tested, qualify for government certification and resale (www3.wipo.int). Regulatory hurdles remain: EFB‑based composts must meet strict composition standards before sale, and testing is ongoing (www3.wipo.int).
Combustion option and energy potential
EFB’s other pathway is power. Fresh EFB’s heating value is only ~10.1–10.6 MJ/kg (wet basis), rising to ~17.5 MJ/kg after thorough drying (www.researchgate.net). One tonne of dried EFB roughly matches the energy of dry wood. Palm mills already burn palm fiber and shells; EFB can similarly fuel mill boilers or combined heat and power (CHP) plants. A Malaysian mill, for instance, installed an 80 t/h steam boiler designed to burn shredded EFB fiber (www.zbgboiler.com).
Indonesia’s total EFB (10–20 Mt/yr) could in principle displace a significant portion of coal/kerosene in mills or local power plants; one analysis suggests total Indonesian palm waste could meet ~10% of national energy, though this assumes optimal collection (www.envirobiotechjournals.com). Boiler programs also depend on water‑side chemistry control to protect equipment; operators consider tools such as oxygen scavengers alongside the core fuel decision.
Moisture barriers and pretreatment
The main hurdle is EFB’s very high water content—typically 50–70% of fresh mass. As one review notes, “high moisture content (in excess of 50%) requires more fuel to be consumed,” severely cutting boiler efficiency (www.researchgate.net). Long‑distance transport is uneconomical because moving so much water (and bulky fiber) costs more than its fuel value (www.researchgate.net). Handling is tricky too: raw EFB tends to mat and bridge in feeders, and its ash—rich in potassium and chlorine—causes fouling. Plants must operate below ~900 °C to prevent slagging on tube surfaces (www.researchgate.net).
To burn EFB effectively, mills typically shred and dry or pelletize it. Simple drying (solar or waste‑heat) can raise higher heating value to ~17–18 MJ/kg, but 40–60% of original mass (water) is removed (www.researchgate.net). Torrefaction or hydrothermal carbonization have been proposed to reduce moisture and increase energy density (www.researchgate.net) (www.researchgate.net). After oven‑drying at 105 °C, one study achieved ~41% energy “yield” relative to raw EFB (www.researchgate.net). Pretreatment adds capital and energy cost, and untreated EFB’s bulk density is very low (a few hundred kg/m³), demanding large hoppers and fans (www.researchgate.net).
Operational trade‑offs and policy signals
Burning EFB can replace fossil fuels (or free up palm fiber/shell) and reduce greenhouse gas emissions by displacing coal/diesel. But because of moisture and ash, the net energy return is modest—wet boiler studies report that firing EFB needs 1.5–2× the fuel mass compared to dry wood. In contrast, using EFB as a field amendment provides no combustible energy but yields agronomic value. Operators decide case‑by‑case: mills remote from plantations may favor energy use, whereas in‑field mulching benefits plantation yield and cuts fertilizer bills.
Policy also nudges choices. In 2024–25, Indonesia limited exports of “palm oil residues” (including EFB) to secure supply for biodiesel blending (www.reuters.com).
Key data recap: fuel use vs. fields
Raw EFB’s high moisture (>50–60%) makes it a poor fuel without drying (www.researchgate.net) (www.researchgate.net). Low bulk density and high ash content also constrain boiler design (www.researchgate.net). If thoroughly dried, EFB’s ~17.5 MJ/kg heating value is reasonable, but drying energy offsets gains. Even so, mills have installed 10–80 t/h biomass boilers to burn EFB (www.zbgboiler.com), with careful pretreatment and handling. By contrast, mulching EFB (10–30 t/ha/yr) can increase yields modestly (2–6%), raise soil organic C by 20–30%, improve water retention and K‑supply (www.researchgate.net) (link.springer.com), and cut synthetic fertilizer use by the majority (≈75% for NPK, biochartoday.com). These practices also avoid open burning (a fire/haze risk) and provide environmental credits (carbon offsets from soil C).
Business calculus: yield, energy, logistics
- Yield vs. Energy: Appropriating EFB for power sacrifices some nutrient recycling. Modeling suggests one hectare yields (~30 t/yr EFB) can substitute ~75% of that hectare’s NPK needs (biochartoday.com) while boosting yields by a few percent (link.springer.com). An equivalent fuel yield (~30 t dried EFB≈525 GJ) only covers steaming needs and doesn’t generate electricity for much beyond the mill.
- Cost and Logistics: Mulching is labor‑ and transport‑intensive (EFB is bulky and wet), but otherwise a free input. Installing boilers or dryers is capital‑intensive and requires continuous fuel supply (limiting location). Mills close to plantations may favor mulching (as Malaysia, Indonesia have often done), whereas isolated mills might burn EFB if nearby farms lack fertilizer access.
- Environmental Impact: Mulching sequesters carbon and avoids open burning. Burning EFB generates CO₂ but displaces coal/diesel and avoids methane from rotting waste. Both pathways are far better than uncontrolled disposal.
Sources: Authoritative studies and reports were used above, including Indonesian sector statistics and peer‑reviewed trials (biochartoday.com) (www.envirobiotechjournals.com) (link.springer.com) (www.researchgate.net) (www.researchgate.net). Regulatory trends (e.g., export controls on EFB) are supported by recent news (www.reuters.com). All quantitative claims reference the cited literature.
