Renewable Energy

Biomasses

Sommario

Biomasses ....................................................................................................................................... 1

Part 1 - Introduction ............................................................................................................... 3

Biological categorization ................................................................................................................. 4

Life cycle...................................................................................................................................... 4

Photosynthetic carbon fixation pathway C3, C4, CAM................................................................. 5

Nitrogen fixation (legumes) ......................................................................................................... 6

Plant cell walls ............................................................................................................................. 6

Plant composition and products ................................................................................................... 6

Focus on biomass composition ........................................................................................................ 6

–Part 2 composition and utilization ............................................................................. 7

Classification on origin .................................................................................................................... 7

Moisture content .......................................................................................................................... 7

Heating value ............................................................................................................................... 8

Classification on supply chains ........................................................................................................ 8

Biomass conversion technologies .................................................................................................... 9

Pre-processing ............................................................................................................................. 9

Conversion to heat and/or power ................................................................................................. 9

Chemical routes to biodiesel from oils ...................................................................................... 10

Biological routes to bioethanol from carbohydrates .................................................................. 10

Thermochemical routes to fuel and power ................................................................................. 11

–Part 3 a focus on proximate and ultimate analyses...................................... 11

Heating value ................................................................................................................................. 12

–Part 4 anaerobic digestion ............................................................................................. 121

Field of application .................................................................................................................... 12

Stage of the overall process ........................................................................................................... 13

Phase of digestion process ............................................................................................................. 13

Factors affecting the process ...................................................................................................... 14

Methods ...................................................................................................................................... 14

Schematic overview of digestion systems ................................................................................. 14

Wet fermentation systems .............................................................................................................. 15

Dry fermentation system ................................................................................................................ 15

Single stave vs multi stage ....................................................................................................... 16

Mesophilic vs thermophilic process ......................................................................................... 16

Role of the nitrogen.................................................................................................................... 16

Role of the pH and alkalinity ..................................................................................................... 17

Advantages and disadvantages of anaerobic digestion .................................................................. 17

–Part 6 pre treatments to anaerobic digestion ................................................... 17

Methods .......................................................................................................................................... 17

1. Biological treatment ................................................................................................................ 17

2. Thermal hydrolysis ................................................................................................................. 18

3. Mechanical treatment .............................................................................................................. 18

4. Chemical treatment oxidation ................................................................................................. 18

5. Hybrid treatments .................................................................................................................... 19

–Part 7 end uses ....................................................................................................................... 19

Composition of biogas ................................................................................................................... 19

Utilization of biogas ....................................................................................................................... 19

–CHP generation otto cycle ...................................................................................................... 20

–CHP generation pilot injection gas motors ............................................................................. 20

Micro turbines ............................................................................................................................ 202

–Fuel cells solid oxide fuel cells ............................................................................................... 20

Biogas upgrading ....................................................................................................................... 21

–Part 8 digestate end uses ................................................................................................ 22

Quality of digestate ........................................................................................................................ 22

Digestate end-uses Italian laws .................................................................................................. 22

Digestate processing for end uses .................................................................................................. 22

Solids separation ........................................................................................................................ 23

Processing of the solid fraction .................................................................................................. 23

Processing of the liquid fraction ................................................................................................ 23

Part 1 - Introduction

Two ways to define biomass:

→ it’s the whole organic matter produced by biological processes.

1. From an ecological point of view

→ it’s organic matter that can be used as a combustible material.

2. From an energy point of view or energy source for power generation, heat of biofuels.

Ex: wood, waste.

Biomass refers both to vegetation found on land or water and to organism able to perform photosynthesis.

Benefits of using biomass

• Possibility to reduce CO2 emissions
• Constant energy over time
• Safe energy supply
• Solution for excess waste problem

Biomass is a renewable resource because the reduction speed of biomass is the same order to the speed used to produce energy.

Relation of speed in three sectors

• V1 = speed in which CO2 emitted to atm as a result of biomass combustion
• V2 = speed in which biomass fix CO2
• V3 = speed in which biomass is transformed in fossil fuels (less rapid than the other)3
• V4 = speed in which CO2 emitted in the atm as a result of burning fossil fuel

NB the source is defined as renewable if the stock has a mass equal to Q=GV product. In this way it ensures that in a certain period of time that resource could be reconstitute.

Q= stock resource for energy production (kg)

G=fraction of the stock consumed to produce energy over a certain period (kg/days)

V= time at which the consumed resource is reobtained (years)

There is no established way of categorized biomass which is defined differently according to the field. Categorization changes depending on the purpose and application. Generally there are two ways to categorized biomass:

• One is biological categorization based on types of existing biomass in nature. There are different categories related to it such as life cycle, photosynthetic carbon fixation pathway, nitrogen fixation, plant cell walls, plant composition and products
• Based on the use or application as resources

Biological categorization

Life cycle

Divided into annual, biennial, perennial plants. Each of them are related to climatic conditions and breeding strategies.

Annual plants (rice) complete their life