At a biofuel terminal, additive injection cannot be treated as a dosing skid that runs on its own. Which additive goes into which stream, and at what rate, depends on the bio-component ratio of the blend, on which part of the blend the additive actually acts on, and on whether the lane blends by ratio or sequentially. Coordination works when the injection controller reads the same meter signals as the blend controller and the dosing basis is fixed before loading starts.
Injector types, the position of the injection point relative to the product meter and general dose verification are covered on the chemical terminal additive injection page. This page looks at how fuel-specification additives are matched to biofuel blends.
Which additives come up in the biofuel chain?
· Antioxidants: Biodiesel (FAME) is susceptible to oxidation in storage. Antioxidants, natural or added, can significantly extend the storage life of neat biodiesel and are best added as close to production as possible. Re-additization at the terminal is preventive only; it does not restore fuel that has already degraded.
· Cold-flow improvers: The low-temperature behavior of neat biodiesel (B100) cannot be managed effectively with current cold-flow additives, which work much better in blends. The source guide notes that conventional cold-flow additives are believed to act only on the diesel portion of a blend.
· Lubricity additives: Blending even a small amount of biodiesel into ultra-low-sulfur diesel improves lubricity; the source states that about 2 % biodiesel almost always gives adequate lubricity and can remove the need for a separate lubricity additive. The exact level depends on the diesel.
· Performance additives for the fossil component: Additives specified by the product owner for the fossil fuel that makes up most of the blend.
What happens to the dose when the blend ratio changes?
This is the central coordination question at a biofuel rack. Additive dosage is normally defined per unit of product volume, but whether that volume is the total blend, the fossil component only or the bio-component only depends on the additive. If a cold-flow additive acts on the diesel portion, for example, a dose held constant against total blend volume delivers a different treat rate to the diesel as the bio-component share rises. On the lubricity side, a bio-component share above a certain level can reduce the need for a separate additive.
That is why the injection recipe should be defined together with the blend recipe. Where one loading arm delivers several blend levels, the controller must hold a separate dosing basis and rate for each blend, and the operator's blend selection should set the additive recipe automatically. Which stream the dose is tied to is settled with the additive supplier's recommendation and the product owner's specification.
Injection point: component line or blended stream?
Injection location | When it makes sense | What to watch |
Fossil product line (upstream of the blend point) | The additive is specified for, or acts on, the fossil component only | Dose is tied to the fossil product meter, so the treat rate on that component holds even when the blend ratio changes |
Bio-component line | Bio-component-specific additives such as antioxidants, when treatment upstream of storage is not available | Terminal treatment cannot repair degraded product; incoming quality should be tracked |
Downstream of the blend point | The dose is defined against total blend volume | Enough line length for the additive to mix before the loading arm |
Storage tank | Preventive tank-level treatment | No per-load traceability; records follow tank movements |
Sequential blending changes the picture: because components pass through the same meter one after another, an additive meant for one component has to be injected while that component is flowing. With ratio blending each component has its own meter, so the additive can be tied directly to the right one.
Control, verification and records
The injection controller takes pulses from the product meters, continuously compares additive flow with product flow and corrects injection in real time when the programmed ratio drifts. Additive quantities, alarms and status can be monitored locally or through the terminal automation system. At a biofuel terminal, keeping the following together in each load record makes any later quality query much easier:
· Blend recipe and the bio-component ratio actually achieved
· Quantity of each additive and the stream it was calculated against
· No-flow, under-dose and over-dose alarms, and whether the load was stopped on them
· Results of periodic checks against additive tank level or a calibration vessel
Storage and pumping temperature data from the additive manufacturer apply to the additive tank and feed line. In cold climates, protection of the additive line should be assessed separately from the main product line.
TLY Enerji's role in additive injection
Depending on project scope, TLY Enerji can support selection and supply of additive and product measurement equipment, integration of injection control with the existing preset controller, PLC or SCADA, installation, testing and commissioning. The additive recipe itself and the choice of additive chemistry remain with the product owner and additive supplier; the supply boundary of the injection system is set through the technical specification.
Information needed for a review
· Additives to be used, target dose for each, and whether it is defined against a component or the total blend
· Blend levels and blending method (ratio or sequential)
· Number of loading arms and the blend–additive combinations on each
· Additive storage conditions and site climate data
· Existing preset controller and the system that will receive additive records
Related pages
· Biofuel blending systems: Control of the blend ratio that the additive recipe is tied to.
· Additive injection for chemical terminals: General injection basics such as injector types and position relative to the meter.
· Biofuel truck loading systems: Cold-flow and storage measures when loading FAME and HVO.
· Biofuel and ethanol custody transfer metering: How load records relate to commercial quantity and component reporting.
Questions on biofuel additive injection
Can a cold-flow improver be added to neat biodiesel?
It can, but the effect is limited. The source guide states that the low-temperature behavior of neat biodiesel (B100) cannot be managed effectively with current cold-flow additives and that these additives perform much better in blends. Cold-flow treatment is therefore usually planned for the blend or the diesel component, while heated storage and line protection remain the main measures on the B100 side.
Do additives lower the cloud point?
Cold-flow additives usually do not change the cloud point; instead they can lower indicators such as the cold filter plugging point (CFPP). For additized fuels, filter plugging test results may therefore be a better guide to low-temperature performance than cloud point. The dosing target follows whichever indicator the product specification limits.
If antioxidant is added at the terminal, will it fix degraded biodiesel?
No. Antioxidant additives are preventive: they can slow further oxidation but cannot remove acids or sediment from fuel that has already degraded. That is why antioxidant is best added as close to production as possible. Additional dosing at the terminal makes sense when it is planned around monitoring of oxidation stability and acid number of the incoming product.
Does a biodiesel blend still need a lubricity additive?
It depends on the biodiesel share and the diesel used. The source guide notes that even low-level biodiesel blending improves the lubricity of ultra-low-sulfur diesel and that about 2 % biodiesel is almost always enough. If the blend ratio can fall below that level, defining the lubricity additive recipe so that it changes with blend level is worth considering.