Lesson 25. Performance evaluation of briquetting machines

Briquetting machine has various sub systems such as drying system, shredding system, dust removing system and briquetting system.

Drying system

Mainly drying of the briquetting feed crop materials will be carried out.  The excess moisture will be dried out in the drying system.  Generally solar based systems will be adopted as drying involves higher cost and will increase the price of briquettes.

In general, the performance of the drying system will be assessed in terms of efficiency of the system, capacity and quality of the final product.  The efficiency will give the better utilization of incoming solar radiation for drying of the crop residues.  The capacity will give the ability of the dryer to dry the residues to the required moisture content in a given time.  The quality of the product deals mainly with the moisture content of the dried crop residues which will be used for briquetting..

Shredding system

This is used to shred the dried mass.  In this system, the dried materials will be size reduced before using in briquetting machines.  The size of the dried mass will be reduced to about 1 to 10 mm.  The out put will be higher with higher size of the material as the work done on the material will be less.  Lesser the size of the material, better will be the briquetting of crop residues.  The efficiency of the shredding system may be improved by having better sharp edged cutting blades, properly maintained rotating parts and well dried crop residues.

Typical specification of a shredding machine

Power requirement            : 10 HP

Production Capacity          : 250 kg/h

Finished product size         : 1 to 10 mm

Raw materials                    : Agro residues

The performance of the shredding machine during the size reduction of cotton stalks, pigeon pea stalks, and soybean stalks are given below.




Red gram

Soy bean


Sieve size





Weight of raw materials before shredding

100 kg

100 kg

100 kg


Weight of raw materials after shredding

86 kg

84 kg

88 kg


Loss of weight during shredding

14 kg

16 kg

12 kg


Percentage of losses

14 %

16 %

12 %


Total time

2.0 hrs

1.30 hrs

2.0 hrs


Power consumption

0.8 kw/hr

0.6 kw/hr

0.8 kw/hr

Briquetting system

The performance evaluation of the briquetting system may be assessed in terms of efficiency of the system, output capacity etc.  The efficiency deals with the input power supplied to the system to the energy spent for the production of briquettes in a specified time.  The quantity of briquette produced in unit time reveals the performance of the briquetting system.  With proper care and maintenance, the specified quantity of the briquette can be produced.

Economic analysis of briquetting system

The economic evaluation of briquetting plant of 500 kg/h for production from briquettes from saw dust is given below.

Machine Cost

            Cost of Briquetting machine (500kg/h)          =          Rs. 9, 00,000

Production Cost

Raw material Cost                                         =          Rs. 1850 / tone

Power Cost                                                   =          Rs.   200 / tone

Labour charges                                              =          Rs.   150 / tone

Cost of loading in gunny bags                          =          Rs.     50 / tone

Cost of maintenance of Machine parts              =          Rs.   110 / tone

Administrative Cost (Cost for supervision)        =          Rs.   250 / tone

Cost of production of Briquette /tone                =          Rs. 2610 / tone

Transport charges of product                            =          Rs.   400 / tone

Net Cost of production                                     =          Rs. 3010 / tone

Sale price of briquettes                                     =          Rs. 3600 / tone

Profit / tone of briquette produced                     =          Rs.   590 / tone


Rated Capacity of briquetting machine                       =          500 kg/h

Production Capacity                                                 =          400 kg/h

Number of Working hours/day                                  =          10 hours

Therefore, Machine outturn/day                                =          4000 kg

                                                                               =          4 tones

Profit/day                                                                 =          4 x Rs. 590

                                                                               =          Rs. 2360

Number of working days per annum                           =          300

Profit/ year                                                               =          300 x Rs. 2360

                                                                                =          Rs. 7, 08,000

Simple Pay Back Period                                             =          9, 00,000 / 7, 08,000  

                                                                                =          1.27 years

(Source : ICAR - NAIP - TNAU - Briqutting Scheme)

From the economic evaluation, it was concluded that the pay back period for the briquetting machine of 500 kg/h producing 60 mm diameter briquettes, working for 300 day per annum is approximately 2 years.



Arun K. Tripathi, P.V.R.Iyer and Tara Chandra kandpal. 1997. A Techno-economic evaluation of biomass briquetting in India, Biomass and Bioenergy, Vol.14 (5/6), pp: 479-488

P.D.Grover and S.K. Mishra. 1996. Biomass briquetting: technology and practices, FAO of the United nations, Bangkok, April 1996.

Last modified: Wednesday, 9 April 2014, 5:07 AM