Biomass Pellet Plant for Crop Residue and Wood Waste in Bulgaria

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Why Bulgaria? 

Bulgaria has significant biomass resources and growing energy demand:

The opportunity: Bulgarian district heating plants are required to increase renewable energy share. Pellets can co-fire with coal and natural gas.

Target customers:

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Raw Materials: Wood Waste and Crop Residues

The client processes three types of raw material:

The client’s challenge: Wood logs (30-40% moisture) need chipping and drying. Sawdust (15-20% moisture) only needs grinding. Straw (15-20% moisture) needs chipping and grinding. The client uses a single line for all three — shared equipment saves capital cost.

Drying requirement: The client’s hand-fired furnace burns self-produced pellets (72 tons/year) to dry material. The dryer reduces moisture from 21% (average) to 12%.

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The Site and Building

The client’s site is in an industrial zone in Burgas. The building is a single-story steel frame structure.

Building layout (3,000m²):

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Equipment Configuration

The client chose a multi-stage biomass pellet production line with shared equipment for all feedstocks:

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Process Flow

This line processes three different feedstocks. The flow changes slightly depending on the material.

Step 1: Raw Material Receiving

Trucks deliver wood logs (from forests), sawdust (from sawmills), and straw bales (from farms). The client stores wood logs and straw in the raw material area (800m²). Sawdust is stored separately.

Step 2: Chipping (for Wood Logs and Straw Only)

Sawdust doesn’t need chipping. Wood logs and straw need size reduction before grinding.

Wood logs (10,000 t/year) are fed into the wood chipper via the infeed belt conveyor. The chipper reduces logs to 2-3cm chips.

Chipper parameters:

• Output size: 2-3cm
• Throughput: 4-5 t/h

Magnetic separator: The conveyor has a magnet to remove nails and staples.

The chipped wood joins the sawdust and straw (which go directly to grinding).

Step 3: Grinding (Hammer Mill)

All material (wood chips, sawdust, straw) is fed into the hammer mill.

Hammer mill parameters:

• Rotor diameter: 660mm
• Rotor width: 1,000mm
• Screen size: 6mm
• Throughput: 5-6 t/h

Step 4: Drying

The raw material is 21% moisture on average. It needs to be dried to <12% for pelletizing.

The ground material is fed into the rotary dryer via the buffer hopper and screw conveyor.

Hand-fired furnace: The furnace burns self-produced pellets (72 tons/year) to generate hot air at 400°C. The hot air enters the dryer.

Dryer parameters:

• Type: Rotary drum
• Inlet temperature: 400°C
• Retention time: 10-15 minutes
• Moisture in: 21%
• Moisture out: <12%

Step 5: Pelletizing

Dried material (<12% moisture) is fed into the pelletizing system via the infeed pit and belt conveyor.

Pre-cleaning: The material passes through a cleaner screen to remove fines.

Pellet mill system (3 independent mills):

Pellettization process:

1. Material is lifted to the distribution screw via bucket elevator
2. Distribution screw distributes material to 3 bins
3. Three pellet mills operate in parallel
4. Pellets exit the mills at 80-90°C
5. Material passes through dehumidifier + dust collector for cooling and dust control

Pellet specifications:

Step 6: Cooling and Screening

Pellets are conveyed to the cooler (natural cooling in the conveyor system. Cooling time: 10-15 minutes.

Screening: Pellets pass through a screener to remove fines:

• Acceptable pellets: 6-40mm → packaging
• Fines (<3mm) → return to pellet mill
• Oversize (>40mm) → return to pellet mill

Step 7: Packaging

Finished pellets are stored in finished bins then packaged.

Packaging process:

• The client uses a bagging scale (automatic)
• Bag sizes: 25kg, 50kg, 1-ton bulk bags
• The client also sells bulk (30-ton truckloads)

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Utilities and Consumption

Electricity breakdown (annual, 300 days, 16 hours/day = 4,800 hours):

Electricity cost per ton: 2,238,000 kWh ÷ 25,000 tons = 89 kWh/ton × 0.20 BGN/kWh = 17.8 BGN/ton ($9.90).

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How RICHI Customized This Line for Multi-Raw Material Processing

The client had specific requirements that shaped the equipment design:

Requirement 1: The client processes three different feedstocks (wood logs, sawdust, straw). They didn’t want separate equipment for each material.

RICHI solution: A single line with shared chipping, grinding, drying, and pelletizing equipment. The client changes the configuration:

• Wood logs: chipper → hammer mill → dryer → pellet mill
• Sawdust: bypass chipper → hammer mill → dryer (optional) → pellet mill
• Straw: chipper (for bales) → hammer mill → dryer → pellet mill

Requirement 2: Wood logs have high moisture (30-40%) and need drying. The client couldn’t afford a large gas or electric dryer.

RICHI solution: A hand-fired furnace burning self-produced pellets (72 tons/year). The dryer uses hot air at 400°C to reduce moisture from 21% to 12%. The furnace cost is low (no complex burner controls).

Requirement 3: The client produces two product lines (wood pellets and straw pellets). Wood pellets command a higher price (higher calorific value) than straw pellets.

RICHI solution: The client runs wood pellets during the winter (higher demand for heating) and straw pellets during the summer (when straw is available from harvest). The same equipment is used for both; the client adjusts the dryer temperature and pellet mill compression ratio.

Requirement 4: The client has 26 staff, running 2 shifts (16 hours/day). They needed a line that can run semi-automatically.

RICHI solution: Three control panels — one for each section (grinding, drying, pelletizing). The client has one operator per shift monitoring the line.

Requirement 5: The client’s building is only 3,000m² — tight for a 5 t/h line with three pellet mills.

RICHI solution: Compact layout: equipment arranged in a U-shape. Raw material enters at one end, finished pellets exit at the same end. The client uses vertical space (elevators) to reduce footprint.

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Product Specifications

The client’s pellets meet Bulgarian standards (based on ENplus, adapted for agricultural residues).

Wood pellets (20,000 t/year):

Straw pellets (5,000 t/year):

Pricing (as of August 2025):

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Market Outlook for Wood and Straw Pellets in Bulgaria

Bulgaria’s biomass pellet market is growing. Key drivers:

1. EU coal phase-down. Bulgaria has committed to reduce coal use. Co-firing biomass at coal plants is the cheapest compliance path.

2. District heating modernization. Sofia, Plovdiv, Varna, and Burgas are upgrading district heating plants. Pellets can replace natural gas.

3. Wood processing waste is abundant. Bulgaria has 3+ million hectares of forest. Sawdust is cheap (40 BGN/ton = $22).

4. Straw is even cheaper. Wheat straw costs 30 BGN/ton ($17) — much less than wood.

Competition: There are 30-40 pellet producers in Bulgaria (1,000-20,000 tons/year). The client’s 25,000 tons/year makes them one of the larger producers.

Challenges the client is managing:

The client’s breakeven point is 15,000 tons/year (60% capacity). At full capacity (25,000 tons/year), the operating margin is about 15–20%. Payback on equipment ($168,000) is about 2 years, and payback on total investment ($1.4 million) is about 4 years.

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Why a Multi-Raw Material Pellet Plant Makes Sense in Bulgaria

Bulgaria has abundant wood waste and crop residues, EU regulations favoring biomass, and a growing industrial boiler market. Here’s why you should consider this market:

Wood logs are cheap (60 BGN/ton = $33). Bulgaria has extensive forests. Wood waste from sawmills is even cheaper (sawdust at 40 BGN/ton = $22).

Straw is even cheaper (30 BGN/ton = $17). The client pays farmers to remove straw from fields — farmers are happy to get paid for something they used to have to dispose of.

The EU supports biomass. The EU’s Renewable Energy Directive (RED II) incentivizes biomass use for industrial heat.

Bulgaria has good logistics. Burgas port (Black Sea) exports pellets to Turkey, Greece, and Romania. Rail connections to Central Europe.

If you’re considering a multi-raw material pellet plant in Bulgaria (or any country with wood processing and grain farming), RICHI can help. We’ve designed lines for wood waste, straw, corn stalks, and other biomass. We understand the challenges (different moisture levels, different fiber characteristics, drying requirements) and can recommend the right equipment for your budget.

Contact us to discuss your project. Tell us about your raw materials (type, moisture, volume), target customers (industrial boilers, district heating, export), site conditions, and budget. We’ll prepare a customized process flow, equipment list, and budget estimate — no obligation.

RICHI Machinery – Multi-raw material fuel pellet plants from 0.2 t/h to 10 t/h. Shipping from Qingdao to Burgas port: 20-25 days. Installation support available in Bulgaria within 2 weeks.