Techno-Guide on Biomass-Fed Furnace/Heater System for Drying Crops

With the development of the biomass-fed furnace/heater system developed at BPRE, mechanical drying becomes an attractive means to drying crops.

The furnace operation is fully mechanically automated, requires very minimal human attention, and reduces health risk posed to operators. It is also a 2-in-1 machine as it produces not only heat but also carbonized rice hull (CRH).

The system specifically promotes the use of rice hull fuel as heat source. Biomass fuel like rice hull is a lot cheaper compared to petroleum-based fuel.

Thus, the technology considerably reduces the cost of drying, making mechanical dryer owners/operators and farmers mutually benefitted. It is also designed to conform to local environmental laws, hence environment-friendly.

Major Components

The biomass-fed furnace/heater system developed has three major components. These are:

Combustion chamber

  • Made of durable materials
  • Insulated with fire bricks
  • Equipped with a mechanism to effect automatic fuel feeding and enhance combustion as well as removal of ash from the furnace.

Heat exchanger

  • Has a cross-flow air tube type heat exchanger
  • Prevents direct contact of hot flue gases with grains being dried. This avoids contamination of dried product with fly ash particulates, smoke and harmful gases.

Fly ash scrubber system

  • Composed of ash tank container that serves as scrubber unit to collect and clean the fly ash coming out from the chimney. With this system, clean smoke and controlled fly ash emission are assured.

Drawing of the semi-commercial BPRE ricehull-fed furnace system (with permission from R.E. Manalabe, inventor)


  • Simple and compact design
  • Fully automatic operation
    • Synchronized fuel feeding and ash discharge
    • Excellent temperature control (“on-off operation”) for any heating application
    • Regulates and maintains uniform temperature


  • Rice hull as main fuel
    • For single dryer – Consumes 23 to 24.5 kg of rice hull per hour
    • For double dryer – Consumes 40.5 to 46.8 kg of rice hull per hour
  • Clean air output (indirect type heating through heat exchanger)
      • Suitable heat source for drying and dehydration of fruits, vegetables, cereals, etc)


    • Space heating and other needs
    • Environment friendly
  • Two-in-one machine
    • Heater (for any heating application)
    • Rice hull carbonizer


Total power 1.125KW, 1 phase, 220 v
Type of dryer
it can be retrofitted
> batch recirculating dryer
> flatbed dryer
> cabinet dryer for HVCC
Fuel consumption > 23-24 kg/hr for 1-batch recirculating dryer
> 40.7-47.5 kg/hr for 2-batch recirculating dryer
Dimension 1524 mm x 1269 mm x 1789 mm
Type of furnace indirect-fired (through the use
of heat exchanger)
Drying temperature 60°C – 70°C for
batch recirculating dryer
Labor requirement 1 operator
BRK-A 110,000.00

Financial Analysis

Taken from the results of pilot testing of rice hull-fed furnace retrofitted to recirculating dryer.

A.1 Added Cost:

  1. Interest on fixed investment, P48,000
  2. Depreciation cost, 67,059
  3. Wage for additional laborer for tending the furnace, 16,500
  4. Power cost (a. Furnace -1,733, b. Ash scrubber – 637), 2,370
  5. Repair and maintenance (a. Materials – 23,331, b. Labor cost – 9,332), 32,663
  6. Kerosene for firing (0.5 li/firing), 1,200
  7. License permit to operate biomass furnace, 1,000

A.2 Reduced Returns: Delayed trade of dried paddy for two mechanical dryers

  • = 9,465.12 kg x 13.00/kg
  • = 123,046.56/year

B.1 Added Returns: Nill

B.2 Reduced Cost, P628,690

  • Cost of kerosene for drying = 1.28 li/50 kg dried paddy x P40/N x 60 batches/yr x 5,116.30 dried paddy/batch x 2 dryers

SUB-TOTAL A: P292,838.56
SUB-TOTAL B: P628.690.00

Incremental change in income (B-A) = P335,851/yr at 60 days utilization/yr for 2 dryers

For more information, please contact:

Bureau of Postharvest Research and Extension
CLSU Cmpd., Science City of Munoz, Nueva Ecija
Tel. Nos. : (044) 456-0213/0290/0282
Fax No. : (044) 456-0110
Email: [email protected]

BPRE Liaison Office
3rd Fir., ATI building Elliptical Rd., Diliman, Quezon City
Tel. No. (02) 927-4019/4029

Ruben E. Manalabe – Inventor and Director II
Postharvest Engineering Department, BPRE

photo from

Leave a Reply

Your email address will not be published. Required fields are marked *